Daisy May Cooper is being haunted. Her first ghost sighting was two years ago – a disembodied pair of child’s legs, running around the bedroom of her new-build house. Then there was an invisible presence, tugging her duvet off her. She’s been hearing voices, too – a Spanish woman, and an ethereal voice in a hospital room offering words of comfort. “It’s like a veil has been lifted,” she says.

You sound crackers, I say. Not something I’d usually voice in an interview – but there’s an infectious, gossipy ease to being in Cooper’s company. “I do! Completely,” she sighs. Then she opens the door of the glass room we’re in, and shouts down the spiral stairs to the photo studio below for her partner to bring his phone up. She wants me to hear something.

One of Cooper’s many talents is surprise. The writer-performer shot to fame with This Country, the mockumentary about rural poverty in the Cotswolds. She showed her range as the lead in BBC/HBO show Rain Dogs, and wrote the twisting female-friendship thriller Am I Being Unreasonable? Her new book, Hexy Bitch, is a twist again. Her riotous account of her occult experiences includes joining a coven that turned out to be a swingers’ club, regressing to a past life, and attempting to have sex with a ghost. The book is funny and often outrageous, yet serious of intent. Having been through extreme experiences in the past few years, she’s grappling with what death means.

The “something” she wants me to hear is a recording of one of the voices she heard. Cooper was severely ill with viral meningitis after the birth of her daughter Pip in 2018. She was alone in a private hospital room, she explains before pressing play. I hear her voice, speaking tentatively into the phone. “If there’s anybody in here … can you speak into the microphone?” The only response is the background hiss of hospital silence. Then, from somewhere else in the room – the tiny sound of a girl’s voice, eerily there and not there. “Don’t be afraid,” it cajoles. Although I’m a cynic, the hairs on my arm stand up. Cooper has the phrase tattooed on her wrist. Whenever she doubts herself, she looks down.

The supernatural has fascinated her since childhood. After her aunt Alison died in a car accident at the age of 30, her mother routinely dragged Cooper to see psychics in the back of pubs. The mediums would sing Roy Orbison songs between performances, and hold a raffle afterwards. Cooper was unmoved by these grasping, hammy shows, but understands why her mother went. “It was her desperation to prove everything wasn’t completely meaningless, that her sister was somewhere.”

Her hope is that technology will advance to the point that scientists can prove there are ghosts. There’s a yearning in the push-pull of her belief. In 2019, she lost her childhood friend Michael Sleggs (who played a version of himself in This Country) to heart failure. Sleggs had endured numerous health problems, including a teenage cancer diagnosis. “He’d been in constant pain his entire life. Even walking caused him pain,” she says. When he was placed in palliative care, “it was horrible, because he was terrified of dying”. Then she received a phone call that changed everything.

Sleggs had had a visitation from an angelic presence, she recounts, which sat at the end of his bed and told him: “In seven days you will have a new body at midnight.” He didn’t know if that meant death or a full recovery – but he told her he wasn’t afraid any more. He died seven days after that, “and his time of death was 11.59”. She can’t know whether angels are real, or if this was a powerful example of bodily self-determination. Either way, she thinks it’s amazing.

“But then I think, why hasn’t he come back, out of everybody?” Doubt clouds her face. There was the presence that tugged firmly on her duvet, on the morning of Sleggs’ favourite local festival. She doesn’t know what to make of that. “If that is you, Slugs, can you please be more specific?” she asks, using his nickname. “Write your name in lipstick on my mirror. I need to know.”

Other famous people have stories, too, says Cooper. Tilda Swinton met someone who practises voodoo, and has warned her not to take it lightly. “She said, ‘This stuff exists, and it’s dangerous, and you can fuck people’s lives up with it.’” Dermot O’Leary’s wife astrally projects “all the time”. The best story she has heard is that of Martin Kemp. While filming in an old Tudor house, the Spandau Ballet bassist saw a woman dressed in 16th-century maid’s clothes, whom he assumed was an extra. “He asked her: ‘Do you know what time lunch is?’ And she disappeared!” Cooper cackles. “Imagine this ghost being like … oh no, not Martin Kemp.”

While ghosts don’t scare her, she is wary of human reactions to her encounters. “It’s isolating, because people think you’re mad,” she says. It’s taboo to say that you’ve had an encounter with the world beyond our own, she notes. “But it exists.”

* * *

The line between worlds must have felt even thinner of late. It’s been just two months since her son Benji was born, seven weeks prematurely. In the middle of filming a second series of Am I Being Unreasonable? in Bristol, Cooper started getting severe contractions, and had to lie down on set. She was taken to hospital, where her waters broke. She was scared – especially when she was given a form to sign indicating that if she died, the family wouldn’t sue the hospital.

Cooper was sent for an emergency C-section, during which she haemorrhaged badly. She doesn’t remember much, apart from the surgeons in scrubs, playing Abba. “I thought, I’m gonna die to Dancing Queen. This can’t be the end.” She didn’t see any lights or angelic figures.

She wasn’t able to meet the baby for two days. He was being cared for in the neonatal unit, in a Perspex box hooked up with wires and a monitor. She describes the “hell” of nurses struggling to administer an IV drip, “trying to find a vein on a baby that small. I was terrified he was going to die.” Walking around the hospital in the grip of fear, she was recognised by other patients, and had to pose for selfies.

She credits her ex-husband’s wife for looking after the children, and her partner Anthony Huggins with looking after her. He’s here today, a calming, blue-eyed presence who now works as her assistant. There’s support for mothers after an experience like that, she says, “but a lot of fathers get PTSD from it. They just feel helpless.”

Happily the family are healthy, and numerous. They live in South Cerney, Gloucestershire with five children under one roof (two each from previous relationships, plus Benji). They navigate a whole spectrum of childhood issues, she laughs, from a three-year-old boy to a 14-year-old girl. Benji has brought the family even closer. “I thought there’d be jealousy, but they do the whole blended thing well.”

Cooper and Huggins met on Hinge. She had recently divorced the landscape gardener Will Weston, whom she wed in 2019. Their three-year marriage, which produced two children, had become strained, and its implosion seems to have imbued both with energy – Weston has since remarried, while Cooper has had Benji with Huggins. They began dating while she was filming Rain Dogs. He had no idea who she was, she reveals with mock outrage. He also told her he worked in advertising, before she discovered his job was putting up billboard posters. During the shoot today, he’d told me the same thing, I say. Cooper storms to the door again and flings it open. She shouts down to the studio floor. “Why are you still telling people you work in advertising?” She returns to her chair. “That’s catfishing. How dare he.”

She had assumed her children would follow in her footsteps, but not so. She thinks her daughter Pip might become a surgeon, comparing her to Saffy from Absolutely Fabulous, the prim daughter of a narcissistic mother. “We’ll be playing Sylvanian families and my heart sinks, because she introduces all these rules. If we were at school, there’s no way I’d hang out with that nerd.” The teasing runs both ways, Cooper reassures. “She speaks down to me in a loving way. ‘Mum, you’ve got to blend your foundation.’ It’s humiliating.”

* * *

Cooper grew up in Cirencester, just miles from where she lives today, in very different circumstances. Her parents struggled financially. At their poorest, Cooper couldn’t afford tampons. She moved between unrewarding jobs – one of which was selling towels at House of Fraser. “I used to steal jeans, perfume. No wonder they’re going into administration.” (She’s behind the curve – it’s been bought by Sports Direct.) Cooper remembers smashing Lindt chocolate Father Christmases on the stockroom floor, to write them off so she could eat them. “When I was a teenager, there was no point in doing any sort of job if I couldn’t steal.”

In her early 20s, a tarot reader told Cooper she would become a famous actor, so she auditioned for and was accepted into Rada. She hated the training. “A lot of these places are run by people who are massively pretentious and bitter that they didn’t make it.” Students were encouraged to instrumentalise their personal trauma in ways that became competitive, she adds, and it struck her as nonsense. “I’m terrible with authority,” she acknowledges.

It was there she met Selin Hizli, with whom she later created Am I Being Unreasonable?. Cooper initially dismissed Hizli as a “wannabe Lily Allen”. The pair had a physical altercation in a lift, before bonding over their mutually unhappy experience of the course. “You hate the people you end up getting on best with, because they remind you of yourself. Maybe that’s just me.”

Hizli went on to play a queen bee character in an early version of This Country. When the series was commissioned, Cooper ghosted her, afraid to tell her the character had been cut. They patched things up, before losing contact again during the pandemic. They’re fine now, but “I’m not a very good friend”, confesses Cooper. She describes herself as intensely conflict-averse. “I’d be a terrible doctor, as I wouldn’t be able to tell anyone they had cancer. I’d just say everything’s great.” She’s been burnt by people using her to further their own careers; moreover, she can’t keep up with the level of interaction expected of friendships. Today she says: “I have one friend, and no phone.”

Her relationship with brother Charlie is, at least, a fairytale. The siblings shared a mattress in London, and an office cleaning job in Cirencester, while improvising sketches based on their childhood. The resulting series was watched by millions and won multiple Baftas, transforming their fortunes. They still squabble, but Daisy, three years older, has always been protective. They anchor each other.

How is Charlie? Living nearby, looking after his own 18-month and three-year-old, and not sleeping. “He looked like a husk before, but now … he looks like a ghost.” He’s too soft, she diagnoses, unwilling to sleep train or discipline his children. The three-year-old in particular is “gaslighting him all the time. He’s getting mugged off by a toddler.”

This Country was the best outright comedy of the decade, and in conversation, Cooper is as hilarious as you’d hope. Even her Instagram is an anarchic joy. Her wilfully obtuse romance with an online scammer, who called himself the Sea Captain, made headlines. There was a series of posts aimed at Penguin Books, arguing her right to insert penises into her autobiography Don’t Laugh, It’ll Only Encourage Her. When she claimed the publisher hadn’t paid her final advance cheque, Cooper commissioned a Tiger King star to record a negotiation video on her behalf, insisting she would “now only communicate through Carole Baskin”.

She seems to have no filter. Does she have any celebrity crushes? “Did you ever watch The Jinx?” she replies. I can only think of the HBO true crime documentary about the real estate heir serial killer. I needn’t have worried – that’s exactly who she’s talking about. “I had a massive crush on Bob Durst. He’s really funny,” she whispers, appalled by herself. “You’re watching him thinking: ‘I’d really like this guy.’”

It’s easy to imagine Cooper at the centre of the showbiz whirl. But wrong. “Because I don’t drink now, I don’t go to parties. I stay at home all the time.” She used to get wildly drunk to combat her introversion, and the pressure to be funny made social situations exhausting. Drink emboldened her, but the hangovers would arrive accompanied by the horrors. “I’d be having flashes of shit I did the night before, thinking … oh my God. Why did I suck that cab driver off?”

* * *

This Country aired its final episode in March 2020. Cooper returned with Am I Being Unreasonable? in the autumn of 2022, a hiatus that sounds fraught. “My marriage was breaking down; I was drinking to get through,” she recounts. The drinking spiralled, to the point, “I was getting up in the morning and drinking vodka.”Cooper has spoken candidly about her mental health crisis during the pandemic, and the challenges of motherhood. The pressure got so much, she was hiding bottles in the toilet cistern, feeling depressed and suicidal. “And I said I need to go somewhere and sort myself out.” She checked herself into a rehab facility for a month, for alcohol addiction issues.

Rehab was “like being in the Big Brother house”, she says – except with a mixed cast of billionaire’s children, overseas royalty and primary school teachers. She found the experience transformative; not to mention a rich character study. “People with addictions are the most creative, interesting, emotionally intelligent people I’ve ever met.”

Cooper writes manipulative characters with rare empathy, from the stalker in Am I Being Unreasonable?, to This Country’s Kerry Mucklowe abusing an elder care scheme to get double dinners. In rehab, she confronted her own tricksiness. One of them had been to buy a bottle of booze and a gift bag to put it in, pretending she had received a present from work. She discovered many of the alcoholics had done the same thing. “I’d thought I was so clever! Pathetic. So funny.”

She’s writing a film about an addiction recovery centre. Two of the patients she grew closest to at the facility she attended have since died of alcoholism, which is why the story is important to her.

Another legacy of rehab is her lack of phone ownership. She had to surrender hers upon checking in, which sounds awful. “It’s brilliant,” she smiles. I guess she now shares a phone with Huggins, to keep up with Instagram, surely a cumbersome arrangement. “I think after the book comes out, I’m going to delete my account,” she says. The general toxicity of social media makes it not worth being on, and like any woman in the public eye, she receives nasty messages. “Lots of it is about the way I look, which I really hate,” she adds. “Some guy saying: ‘Your bottom teeth make me want to barf.’ It’s just bullying.”

Last year, Cooper received compliments for her dramatic weight loss, yet the reality is complex. “People are like, “Oh my God, you’ve lost so much weight’, but I had always been slim before. That’s what people don’t know.” She had been larger during This Country, and part of her glow up was simply coming off the antidepressant quetiapine. She describes its side-effects as slowing her metabolism to a crawl and giving her the munchies, which caused her weight to balloon. She appreciates the irony. “Aren’t these supposed to be antidepressants? Now I hate the way I look.”

She calls herself lazy, but is actually what’s known in writing as a “pantser”. “I have to find it in the last minute,” she confirms. A high-pressure process, for a slate as packed as hers. In addition to the rehab film, she’s currently finishing the second series of Am I being Unreasonable? while a third has already been commissioned. There’s a TV project subject to secrecy, but which will be one of the most discussed of the year. She’s also adapting Hilary Mantel’s funny ghost novel Beyond Black, with the Skins and His Dark Materials writer Jack Thorne. Before she died, Mantel said she wanted Cooper to play the part of the travelling medium. It’s a perfect fit – mixing domestic mundanity and gothic horror, to expose the psychic underbelly of the suburbs. This Country, through a glass darkly.

It’s hard to imagine she has any time left over, but Cooper also develops new writers, especially those without class advantages or industry connections. There are amazingly creative people who aren’t being reached, she says. She describes a catch-22, in which production companies don’t accept unsolicited scripts, but where it’s hard to get an agent without interest from production companies. Broadcasters, too, could do more to bridge the gap. “They make it feel very guarded.”

Altruism has its downsides, though. One man recently sent her a seven-novels-length account of his time working at Co-op, in which nothing happened “apart from getting into work at two minutes past nine, and reducing some grapes”. Sounds a bit Knausgård. In an effort to be more organised, Cooper is starting her own production company.

Her advice to new writers is simple. “Me and Charlie came from such a poor upbringing. We were always going cap in hand to people,” she says. She urges creatives to protect their voice, even when it risks a project not going forward. “You’ve got to swing your dick around,” she says. “Don’t feel inferior to anybody.”

Cooper no longer has to worry about money, yet she credits her current wellbeing less to material comfort than confrontations with the immaterial. Her recent visitations, the bizarre sightings and ethereal voices, have had a profound impact. “I used to get terrible anxiety, and I sort of … don’t now. I feel more at peace.”

It sounds as if she is talking about faith. She doesn’t describe herself as religious – too many terrible deeds have been committed under that name. But she’s aware there’s a broad, existential dimension to her paranormal preoccupation. Everything changes, she muses, once the question changes from an if to a what. Specifically: “What is all this? What’s the meaning of being? What’s our purpose? We’re so naive to think there’s not a bigger picture.” She sounds lost in wonder, and for the first time in the conversation, there is a lapse into silence. We’ve butted into the big question, perhaps the only one that matters. I may as well ask. Ultimately, what is the meaning of life?

She doesn’t skip a beat. “Fuck knows.” We both burst out laughing.

• Daisy May Cooper’s Hexy Bitch: Tales from My Life, the Afterlife, and Beyond is published on 24 October by Radar (£22). To support the Guardian and Observer, order your copy at guardianbookshop.com. Delivery charges may apply.