“It takes a lot for Nicole Scherzinger to burn out,” says Nicole Scherzinger, X Factor judge, Broadway singer, Pussycat Doll, and celebrity face of yoghurt; and I believe her. “In the past I’ve said you can never work too much.”

We are at the Rosewood hotel in Holborn, London, picking up where we left off a few days ago, when our interview had ended after half an hour due to a meeting being brought forward. Scherzinger had only just returned to London from presenting at the MTV Europe music awards in Spain the previous night.

When we first met, I had asked Scherzinger, 41, how she defined herself; what the through line was in the projects she took on, from Lloyd Webber to Müller. “How I define myself?” she had repeated incredulously. Then she had said she was “very relatable”, and I’d hoped my scepticism hadn’t registered on my face.

Stars love to claim that they are just like us, but Scherzinger’s quotidian glamour – her authoritative presence on The X Factor; her ubiquity on red carpets and in the tabloids, for years as Lewis Hamilton’s girlfriend – had made it seem more of a reach for her than others. When, in 2005, the Pussycat Dolls’ Don’t Cha had been inescapable atop the charts in 15 countries – as in, “Don’t cha wish your girlfriend was hot like me?” – I had related to the girlfriend.

But today I find Scherzinger engaging company over a cup of mid-afternoon tea: unflinching, unapologetic, revealing shades of her surprise conservative streak and the “goofball” she assures me she can be. Legs curled up beneath her on the sofa, snakeskin stilettos kicked to the side, she is visibly more relaxed than a few days ago, and excited about going to see Lizzo perform later on.

She does not call herself a feminist (“I’m just for women. I’m also for the human race in general”) but Lizzo, she says, is carrying “the torch for female empowerment” that Scherzinger held 14 years ago with the Pussycat Dolls. “I would say: ‘Inside every woman is a Pussycat Doll, inside every woman is a Lizzo.’”

Don’t Cha by Pussycat Dolls ft Busta Rhymes.

The Pussycat Dolls were unleashed into the world in 2005, presented on their debut album PCD as a playfully predatory gang, with Scherzinger the ringleader. As lead singer, she was the only one of the six to gain mainstream name recognition, reportedly a consistent source of tension within the group, and a factor in its dissolution after two albums in 2010.

Scherzinger speaks fondly of “the Dolls”, but is upfront and unapologetic about playing a bigger part than the rest of the band. “I pretty much executive-produced those records. That music felt like my music.”

Now, after years of speculation, the Pussycat Dolls are reuniting for a UK tour in 2020. How does Scherzinger think Don’t Cha will be received in this era of mainstream feminism, when pop stars are more concerned with building women up (if sometimes superficially, at least) than stealing their boyfriends? “I feel like it was the catalyst, like we were at the forefront of all that. I still think that song is a classic and it holds just as true today, the power behind it.” Scherzinger shrugs: “And it’s just fun, not taking yourself too seriously.”

I’m a massive fan of all the cool kids out there, I’m not going to judge them. I try to be a little bit more … classy Nicole Scherzinger

She traces the Pussycat Dolls’ lineage back through the Spice Girls’ girl power and the “empowering” pop of En Vogue, TLC and Destiny’s Child(I Don’t Need a Man, which Scherzinger wrote, was inspired by Independent Women Pt 1). But the Pussycat Dolls – one of the best-selling girl groups ever – were also peculiarly of their time, radio-friendly hits driving their profile and album sales in a way that no longer seems possible in the streaming era.

“We had quite a machine behind it, so things happened very focused and very fast,” says Scherzinger. “They had their perfect candidate right here, because I am a workhorse. I just rolled up my sleeves, got in the studio and turned out these records. Before we were done, we had hits coming out.”

Scherzinger – then fresh out of Eden’s Crush, a short-lived girl group assembled through the US version of Popstars – had been recruited to the Pussycat Dolls from a cold audition. Founding choreographer Robin Antin and the record industry executives working to turn her dance group into a band agreed to see Scherzinger as a favour to her lawyer.

“I don’t have a good memory, and I remember that audition like it was yesterday,” she says. “They were rolling their eyes anyway, they only let me take two steps into the room. I pretty much sang an original song a cappella, standing next to the door. All I had to go on was my talent for singing.” And an original song, too. “Yeah,” she says quietly smiling to herself. “Guess I got balls.”

The Pussycat Dolls’ hyper-sexualised image also captured the collective imagination. Reviews condemned or celebrated the “fantasy of a girl group that’s only in it for sex” (to quote from one that was very much in favour). The fact that they had been assembled from a burlesque dance troupe rarely went unremarked upon in their press.

Scherzinger rolls her eyes at the reminder that they had been fined for public indecency while performing in Kuala Lumpur. The group’s reputation and “cabaret vibe” drew a lot of attention, she says, “but if you look at my outfits, I was in trousers most of the time”. She has never even kissed anyone in a music video, while now, “people sucking each other’s faces off and dry-humping – it’s everywhere, you know?”

She mocks herself a little for clutching her metaphorical pearls – while drinking tea and wearing a cardigan – but admits that a part of her is quite traditional. “I think there’s something to be said for leaving a little bit for the imagination. I’m a massive fan of all the cool kids out there, I’m not going to judge them. I just know, for myself, I like to try to be a little bit more … I don’t want to say demure, I sound like a prude – classy?”

Although Scherzinger was born in Honolulu (and is of Filipino and Hawaiian-Ukrainian descent), she grew up in Louisville, Kentucky, and was brought up Catholic; she says she still attends church at least twice a week, either in person or online. “I was very conservative. I had really strong religious beliefs. I just wanted to make my mother proud.”

She remembers, before her audition, being intimidated by other women dressed only in their underwear; she had only ever performed in lingerie while playing Velma Kelly in her college production of Chicago. “In the beginning, it was a massive hump for me to get over,” she says of the Dolls’ determinedly sexy image (or “joyous carnal celebration”, as that review put it).

Nicole Scherzinger: ‘I set such high expectations, I want to be on my 15th world tour’ Photograph: Pal Hansen/The Guardian

Scherzinger’s struggle with an eating disorder and body dysmorphia predated the Dolls, but the image-consciousness of the group – combined with the pressures of fame and her work schedule – exacerbated it. She would sometimes go to the gym for five to eight hours a day and she obsessed over food. “A lot of that stole the joy of what I was doing, because I was living in a very dark world. I was either working or tormenting myself.” That is why she says she has always been in favour of a Dolls reunion: “I didn’t get to enjoy it before.”

Her body image became an addiction, she says; she would wake up on the bathroom floor, having passed out from “not taking care of myself”, as she puts it. She saw doctors, but it was only towards the end of the Dolls, when Scherzinger was in her early 30s, that she started to put her issues behind her. She had been told that her bulimia was affecting her vocal cords: “It was a real awakening for me.” She saw more doctors, she did therapy, “but in the end it has to be yourself”.

“We all have a choice,” Scherzinger says firmly. “We can choose to beat ourselves up or go back to those old patterns, or we can choose to learn and grow and evolve and be like: ‘I’m going to have to rewire my brain’.” She returns regularly to this theme: that self-love, success, even happiness are all down to a decision, then determination.

That narrative, of the triumph of the individual is also a cornerstone of The X Factor, of which Scherzinger has been a fixture in the US and the UK since 2011. Scherzinger put together One Direction as a guest judge at the show’s peak (“I remember saying: ‘They will be undeniable to girls’”); now The X Factor: Celebrity is registering its lowest-ever ratings. Can the format still make stars?

“Absolutely,” she says. “This is still a massive, huge platform. And then afterwards, it’s up to the contestants. Little Mix are so successful because those girls worked their little tushies off.”

Little Mix’s Jesy Nelson struggled under the spotlight, particularly with online abuse; does she think that contestants are supported enough? “I mean, you can’t baby these people,” says Scherzinger impatiently. “It’s like, they’ve already given you a platform; this overnight success that you’re getting is what people have taken their whole lives to achieve, and some will never even get there.

“It’s not going to be a walk in the park. Anything that’s worth having is going to take work.” Her tone softens. “And it comes with it, unfortunately – we all deal with it.” So Scherzinger has struggled with online abuse herself? “Yeah. I just don’t go on the friggin’ internet!”

I’m a pretty tough cookie. The only thing that can burn me out is emotional stuff Nicole Scherzinger

The most sexism she has ever encountered has been while in the company of high-profile ex-boyfriends, she says; Lewis Hamilton is implied, although she does not identify him by name. “All the guys worship them, then they look at me like I’m on the bottom of someone’s shoe. The way that people looked at and treated them, and then how they looked at and treated me by his side; I just thought it was sexist. It made me pissed off.”

It is not as if she has not been tested. The week before we speak, in early November, her cousin was killed in a hit-and-run accident in Florida, and “because my mom took on the stress of that, she was put in the emergency room,” she says. “I’m a pretty tough cookie. The only thing that can burn me out is emotional stuff. And honestly, this past week was probably one of my hardest weeks of my life.”

Her mother is in a stable condition now, but her cousin’s killer has still not been identified, says Scherzinger, growing tearful. “It’s just a horrible thing that I would never wish upon anyone else, and it haunts me every day that … um,” – she pauses for a long time, her voice cracking – “we have no justice for him yet. It’s hard to think that someone can take someone else’s life. I think we all hold responsibility, in everything in life. I’m mostly sad because I’ll never have my cousin back.

“It really puts things in perspective. Guess what happens when you die?” She meets my eyes with fierce focus. “Nothing. Nothing else will ever happen to you, because you’re dead. And that’s a huge awakening, because that means you get one life.”

Scherzinger draws evident satisfaction from defying others’ expectations, remembering with pleasure Simon Cowell’s look of stunned disbelief after seeing her perform: “I was like: ‘You’re a little late to the Scherzi party.’” They are great friends; he has been kind to her after her cousin’s death, she says. “I was probably a bit afraid of him, but now? Nuh-uh. Now I’m very headstrong about my views and what I have to say.”

Doll parts … Nicole Scherzinger as Grizabella in Cats. Photograph: Tristram Kenton/The Guardian

Yet Scherzinger’s own career as a solo artist never quite took off, peaking with Don’t Hold Your Breath in 2011 (which knocked Someone Like You by Adele from UK No 1). Several albums were scrapped at her request, totalling about 500 songs that no one has ever heard. Scherzinger chalks that up to being a perfectionist: “My mother said when I was a little girl, if I coloured slightly outside of the lines, I would rip the page and throw it across the room.”

Would she like to be a star on Adele’s level – or Lady Gaga, who toured as Pussycat Dolls’ support? Scherzinger looks at me like it is obvious. “Oh, absolutely. It’s been for ever since I’ve put out music, and that’s difficult for me, especially when I always set such high expectations for myself. I want to be on my 15th world tour.”

The fact that she isn’t, Scherzinger says, is partly a reflection of her social anxiety and her reluctance to be “more of a fame whore, as people call it”. “My team has to wrestle me to to the ground to get me on a red carpet … I’d much rather just be at home, eating jambon.”

But she is working on new music, and diligently sets deadlines to ensure that her personal goals don’t fall by the wayside. In late October she staged two intimate performances for about 150 members of the Broadway community to showcase another side of her as an artist, with plans to repeat it in London. Scherzinger was nominated for an Olivier award for her turn as Grizabella in the West End revival of Cats in 2014, and was set to reprise the role on Broadway two years later before pulling out at the last minute. Scherzinger would have loved to have been in the Cats film, she says, but the casting director refused to see her audition. “That really upset me, I won’t lie about that. I was devastated.”

Andrew Lloyd Webber’s wife Madeleine comforted her over the phone, the couple being “like family” to her in London, she says (Lloyd Webber’s “absolute twot” comment behind them, then). “I just wanted to be given a fair opportunity – then you can turn me down. Turn me down to my face, at least, and they didn’t.” In that light, I say, the Broadway nights seem like she is getting her own back. She smiles, the Pussycat that got the cream. “Hey. It will be.”

The Pussycat Dolls’ UK tour starts on 5 April 2020. Tickets available from livenation.co.uk