Mariah Carey is the most famous, or infamous, diva in the music business. And today she doesn’t disappoint. When I ask whether the outlandish stories about her are true, she becomes spectacularly diva-ish about her own divadom. “Are there myths about other people and their diva-ishness?”’ she asks. Of course, I say – but not as many. “So I have more myths about the diva-ishness?” Yes, but I’m trying to find out if they are true. OK, fire.

Is it true you once asked for 20 white kittens and 100 white doves as a rider? (In 2009, it was reported that this is what she had asked to be surrounded with when opening the Westfield shopping centre’s Christmas lights, but she was turned down on health and safety grounds.) “No, 20 cats is an absolute lie. I’m not a cat lady. I don’t have one cat any more.” Fair enough, I say. Do you insist on a new toilet seat and gold taps whenever you stay in a hotel? “I mean, honestly? Golden taps! I could just buy a house for that!” Please, can this next one be true – your reputation is at stake: do you only bathe in French mineral water? “No, I bathe in milk.” Really? “Yes, sometimes I use milk as a beauty treatment. I don’t want to give away all my secrets.” Hot or cold? “‘Cold milk.” So the mineral water is not true? She smiles. “Well, I guess if there’s no clean water and I had to use mineral water, maybe I would.”

This comes towards the end of one of the strangest interviews I’ve ever done. When I first arrive, the waiting room is so cold I’m convinced Carey’s team will only let me meet the Queen of Christmas once I’ve been cryogenically frozen. It’s a gorgeous LA day out there, but this is Planet Mariah. Brrr.

The room gets colder and colder. I’m still waiting. Eventually, an imposing woman whisks me upstairs. “Mariah will answer no personal questions,” she says. “But you can ask her anything – anything – to do with her upcoming Christmas tour.”

A giant of a security man blocks my way. “Yeah, all the interesting stuff,” he says, without irony. Jesus. I’ve just flown from London to LA at a few hours’ notice to meet the great Mariah Carey to discuss … her Christmas tour, and nothing else. There is no time to argue.

I am led into the interview room. Only it appears to be a film studio – camera operators, producers, makeup artists, cushion primpers. But I can’t see them clearly. The room is dark. At the end is Carey, sitting like a waxwork on her throne.

My chair is opposite her, but about three metres away. If I lean forward and stretch my arm out, I’ll still be touching thin air. There is a flurry of whispers and panicked activity. Carey is unhappy. I am moved, then returned. She is every bit as poised – only on a new throne.

Carey, 48, looks Jessica Rabbit fabulous, but I wish I’d brought my specs. I can make out a tight red dress and rocks galore – two huge butterfly diamond rings, diamond necklace and bracelet. Even her sandals are sparkling.

It’s great that you’re coming to Britain for the Christmas tour, I say. She smiles graciously. “Thaaaaaaaank you,” she says. “I’m so excited, especially coming to Britain at Christmas time is gonna be so special. I feel it’s one of those places you like to be during the holidays. I mean, it’s great all the time, but the holiday period is especially festive.”

Keep on topic. Her team’s orders ring in my ears. What will you be bringing to the Christmas show? “I’m bringing everything I can for Christmas. It’s really about the music and being with the fans at Christmas time. I’m trying literally to spread good cheer to people who come to the show.’”

Behind Carey, I can make out a huge Christmas tree. It’s 1 June. To my left and right, her team are standing and kneeling, faceless shadows in the dark, ensuring I stay on topic. Will there be reindeer at the show? “I can’t respond about the reindeer. I’m definitely gonna have reindeer in my house at Christmas.”

Silence.

Carey, Nick Cannon and their children. Photograph: Startraks Photo/Rex/Shutterstock

Her people told me that although she doesn’t do personal, she is happy to talk about being a proud mom. She has seven-year-old twins, Monroe and Moroccan, with her former husband, the actor and comedian Nick Cannon. Do the kids like Christmas? “They luuuuurve Christmas. They’ve met Santa Claus.” What did he say to them? “He told them not to use bad language.”

Silence.

Two minutes in, we’ve exhausted Christmas. I swallow loudly. She smiles. Are the twins like you, I ask. “They both have traits. My son is a little bit bossy.” Does he get that from you? “Bossiness? Not on his level, no. He’s next level. I’m not that bossy, honestly. I try to be nice. I doooo,” she coos. Then her tone changes. “I know everybody thinks I am. Whatever. I don’t know what they think. I don’t care.” Do you think there are lots of misconceptions about you? “Yeah, I do.” Such as? “I don’t know and I don’t want to know. If I looked at every single thing people say about me I couldn’t exist as me, so I’d rather just see certain things.”

Carey is not merely Queen of Christmas, she is pop’s record record-breaker – the first star to have their first five singles top the US charts; the most weeks at No 1 in the US singles charts alongside Elvis Presley (79); the only artist to have had three singles debut at No 1 (Fantasy, One Sweet Day with Boyz II Men and Honey). One Sweet Day spent longer than any other single at No 1 in the US (16 weeks). Merry Christmas is one of the bestselling Christmas albums of all time (15 million and counting), and her joyous All I Want for Christmas Is You is the bestselling Christmas single in the US (in the digital era). Her vocal pyrotechnics inspired a generation of singers to perform big (see just about every female singer on a TV talent show).

She was born in New York state to a white Irish-American mother and an African American/Afro-Venezuelan father – Patricia was an opera singer, Roy an aeronautical engineer. But they divorced when she was three and her mother struggled to make ends meet. They moved numerous times for work, money was in short supply and family life was turbulent. Her older sister Alison developed a drug problem, had a baby at 15, went into sex work and became HIV positive.

Carey’s wedding to Tommy Mottola in 1993. Photograph: Ron Galella/WireImage

Carey has said she sang and wrote songs from an early age to escape. At 12, she was working in studios as a backing vocalist. At 19, she was discovered by the Sony boss Tommy Mottola. Carey wangled her way into a party attended by record executives and handed Mottola a tape. He listened to it on his way home, and rushed back to find her. But she had left. Mottola spent two weeks tracking her down. He signed her up and spent two years working with Carey on her first album, released in 1990; it produced four No 1 singles. Her voice had an incredible five-octave range, the music often winsome – designed for white teenage girls. In 1993, Carey and Mottola married – she was 23, he was 20 years older. Carey’s life was called a Cinderella story. When she and Mottola split up four years later, she claimed he had been controlling and compared married life with him to being imprisoned at New York maximum security jail Sing Sing. He denies the claims.

I ask if she supports the #MeToo movement. “How can I not? I’m all for people speaking their truth.” Have you experienced sexual harassment in the work environment? “I have.” How have you coped with it? “Like I try to cope with many things by turning a negative into a positive. Even if it’s just escaping an awkward moment.” Were they just moments or something more sustained? “A bit of both, but I definitely don’t want to get into it in this interview, so don’t hate me, darling!” Carey’s natural voice is rather gravelly. But now she is channelling Marilyn Monroe.

#MeToo is not simply about sexual harassment, it’s about exposing controlling men, I say. “I have experienced that, yes,” she says with a tight smile. In your first marriage? “Other occasions as well. But that had less of an impact on my life than being in a completely controlling relationship.” Did it strengthen you? “Yes, but it also wounded me. When you have to control your own emotions constantly and be aware of every move you make and pretty much ask permission to exist it affects your life.”

The split with Mottola also marked a change musically. She became more adventurous, recording with rappers Jay-Z (Heartbreaker), Snoop Dogg (Say Somethin’) and Ol’ Dirty Bastard (Fantasy). Was divorce liberating? “I was definitely more free. But that started a bit before. Fantasy with ODB happened when I was still in that relationship. There were a lot of things that felt liberating, but it was also a battle because of being embroiled in the business when you’re in a relationship.”

She might be reluctant to answer questions about her personal life, but she can’t help herself. Carey is by nature a talker – emotionally literate and open. In April, she faced her own allegations when her former manager Stella Bulochnikov, until recently a close friend, said she was suing Carey over breach of contract. She also claimed the singer sexually harassed her. I ask Carey if she wants to comment. She glares at me incredulously. “I can’t talk about it, but I think you can see on my face what I think about it.”

One of the shadows turns her index finger in rapid circles. The message is clear – change the subject. Now.

I ask Carey what music she most likes to listen to. “Silence!” she says. She bursts out laughing. As do the shadows. Suddenly the room is full of giddy, screw-you laughter. It’s a good putdown. This is the Carey I like – acidic, sharp-tongued, direct. She pauses. “No, I’m just kidding. You have to write that I’m just kidding. Hahahaha!” Or what? “Or I will hunt you down.” She pauses. “That’s a lyric from one of my songs.” She finally answers the question. “Stevie Wonder is my favourite artist of all time, and Aretha Franklin is one of my favourite singers ever. I love Prince, Michael Jackson.”

On the Sweet Sweet Fantasy tour in 2016. Photograph: Jim Dyson/Getty Images

Not surprisingly, her professional relationship with Sony deteriorated after she and Mottola divorced. In 2001, she signed for Virgin Records in a huge deal – $100m (£75m) to make five albums. But the first album, Glitter, was a relative flop (accompanied by a disastrous film) and the deal was terminated, although Virgin had to pay $28m for the privilege. In 2005, she returned on Island with a massive album, The Emancipation of Mimi; the single We Belong Together was No 1 in America for 14 weeks and named song of the decade by Billboard. Since then, her career has dipped. Her last album, Me. I Am Mariah … The Elusive Chanteuse, released four years ago, failed commercially. It is nine years since she had a solo hit single. Doubtless she would tell the world that she is still big, it is the music industry that got small. She corrected a reporter who said she had been paid $12m to be a judge on American Idol in 2013 (which she described as the worst experience of her life). The true figure, she said, was $18m. Carey is worth an estimated $520m.

It is interesting that she mentioned Jackson and Prince as two of her heroes. They also struggled to cope with extreme fame. Two months ago, Carey revealed she was diagnosed with bipolar disorder 17 years ago and talked about her continued struggle. This came three years after a former friend told the Daily Mail that she “lived in a bubble” and that “the biggest byproduct of fame is that it makes people almost bipolar”. Does she agree? “There is a price to pay for living a public life. You can either sit there and go ‘Woe is me, I’m famous!’, which some people do. But you kinda asked for it.”

If she could track the roots of her bipolar disorder back to anything, she says, it would be an identity crisis in childhood. “It was a combination of being biracial and experiencing the darker side of life. My mom experienced a lot of racism as an opera singer because she was married to a black man. Again, it’s impossible to encapsulate that in this setting.” She tells me she is writing her memoirs and all will be revealed.

Her mother’s own family disowned her for marrying a black man. How did that affect her mother? “She was very active in the civil rights movement. She marched with Martin Luther King.” As a child, many people assumed Carey was white. I mention a story she once told about a friend coming to her house when she was a little girl, meeting her father and screaming. “She burst into tears because she had never seen a black person. I just remember how that impacted on me.” Did you wish you had darker skin? “Of course! But what can I do? I can’t go in the sun. I had to go through so much in my childhood just to feel accepted and feel worthy of existing on Earth because I felt so different from everybody else growing up, because I was biracial, because I was so ambiguous-looking and because we didn’t have the money to escape whatever the everyday realities of life were.”

She says she has always struggled to believe in herself. “I have very low self-esteem.” Has there ever been a time when you unambiguously liked yourself? “I like myself when I record a song and listen back to a bit and feel good about everything about it. There’s a sense of accomplishment in the work.”

In 2001 Carey made a memorable impromptu appearance on the MTV show TRL. She turned up, uninvited, on the live show with an ice-cream cart, and shocked the host by removing her top and handing it to him. Soon after this, she announced she’d had a breakdown and was “under psychiatric care”. This was when she was first diagnosed with bipolar disorder. Many people with mental health problems will draw strength from you speaking out, I say. “Well, that is the goal.” Were you worried about making it public? “I wasn’t excited about having to talk about these details of my life. I wasn’t thrilled. But again, what you’re saying to me about other people finding some kind of strength from that is the most important thing.” Why did you decide to go public about it now? “I wanted to be more free to be who I am.”

On stage in Los Angeles last year. Photograph: Tommaso Boddi/Getty Images for AIDS Healthcare Foundation

Carey once said that after signing her first major record deal, she couldn’t sleep for more than two hours. Was that because of the pressure to succeed? No, she says – again, it goes back to her childhood. “I’ve always had sleep issues. I remember being six years old and not being able to fall asleep. There was always something going on in my house when I was little so I never really felt safe. I think that started it.”

Among the many people she appears to have fallen out with is her sister Alison, who complained that Carey has given her no financial support while she has been desperately ill. Alison also claims that the money she earned from sex work was used to subsidise the family, and paid for the outfit Carey wore when she first met Mottola.

Did what happened to Alison as a teenager scare her? “Absolutely. It turned me into a very guarded person, and a very prudish person on a lot of levels.” Does she feel guilty that she enjoyed such success while Alison struggled through life? “Well, I don’t think it’s for me to feel guilty about decisions that other people made with their lives. I do as much, privately, as anybody would do for people who have not been very considerate of me, to put it mildly.”

The Shadow-in-Chief is making circles again. So I change the subject. Carey once said: “I went from one semi-psychotic guy to the next.” Does she have dodgy taste in men? “Oooooh … possibly. That could be one assessment. I have to take the blame for it.” Who has been the best man in her life? She takes her time. “I gotta go with my son. He’s not a man yet, but he will be one day. I have high hopes for him.”

Her second husband, Nick Cannon, suggested Carey’s romance with her backup dancer/choreographer Bryan Tanaka was confected for her recent reality show. Is it a real relationship? “Yes.” Is it love? “I’ve been trying not to talk about it, and all you do is push me more and more. And then you wonder why I have low self-esteem. You don’t listen to a damn thing I say. Hehehehehe!” Her laughter is wholehearted, but the Shadow-in-Chief is making circles.

A voice shouts: “Last question!” What do you think of Donald Trump?

But she doesn’t have a chance to reply. “OK, we’re done,” the voice says. “Thank you so much Simon. I appreciate it.”

I walk up to Carey to thank her. But the imposing woman comes between us.

“‘You weren’t supposed to ask a lot of that,” she says.

“It’s my job,” I reply.

“I know, but I’m trusting you to tell it properly.”

Well, if I don’t, Mariah can always hunt me down, I say.

“I will hunt you down,” Carey sings quietly at me. And then, puff, she disappears into the darkness.

Mariah Carey’s All I Want For Christmas is You tour arrives in the UK in December, livenation.co.uk