One afternoon in March 2012, Simon Cowell was taking a cigarette break backstage at Greensboro Coliseum in North Carolina, where he was judging auditions for the American X Factor, when he came across a girl lying on the ground, sobbing.

The girl was Camila Cabello. She had just turned 15, and for her birthday had asked her parents – Cuban immigrants living in Miami, who were making ends meet as a shop assistant and car washer – to drive her the 12 hours from their home to the auditions. Cabello explained to Cowell that, having been kept waiting for two days to see the judges, she had just been told by the producers that time had run out and she should go home.

“Apparently she was a reserve,” Cowell tells me over the phone. “So I said to her, ‘Listen, I’ve got no idea what you’re talking about, or what a reserve is, but since you’re here, come and audition.’ Five minutes later, she sang [Aretha Franklin’s Respect] in front of 7,000 people, and it was sensational.”

Cabello has a pint-size frame and a gigantic, intoxicating voice. What it lacks in technical finesse it makes up in youthful passion and romantic melodrama. Cowell installed his charismatic young discovery as the (unofficial) lead singer of a group comprising four other female contestants, and Fifth Harmony was born. After finishing the competition in third place, they signed to Cowell’s Syco label, becoming a sort of sister act to his other X Factor protégé group One Direction. Within months, Fifth Harmony had racked up a platinum-selling debut album of chart-friendly feminist anthems, a sold-out world tour, two performances at the White House and tens of millions of young fans.

For Cabello, that was just the start. Last year, Havana, the second single from her number one debut solo album, came to define the summer – a rare feat in an era of streaming overload, where every hit is usurped by the next within days. An ode to the city where she was born and raised, featuring slow, sensual vocals layered over a Cuban-style piano riff, Havana made the singer the first female artist to achieve a billion streams for a single song. Whether or not you’re a fan of Cabello, you’ll have heard it.

This summer, the 22-year-old has repeated the impossible. Señorita, a Latino love song from her imminent second album featuring fellow pop star (and, as of July, boyfriend) Shawn Mendes, has once again conquered the charts. Talk about power couple: according to Spotify, the online music-streaming service, 21-year-old Mendes and Cabello, who picked up two MTV Video Music Awards for Señorita last week, are the most listened to artists in the world after Ed Sheeran. “Havana was a once-in-a-lifetime kind of success, and she’s just… done it again,” says Cabello’s manager Roger Gold, who first met the singer while serving as Fifth Harmony’s lawyer. “We never thought it would be this massive.”

When I repeat Gold’s words back to Cabello over an oh-so-millennial oat milk latte in a vegan café in Montreal – the latest stop on Mendes’s world tour – she grins. “It was the same with Havana,” she says, keeping an eye on the windows for the fans that have been camped outside her and Mendes’s downtown hotel since the couple were photographed ambling adoringly around the city together the day before.

“Everyone said to me, this is a Latin song, it could never be the single. Label heads and friends were saying I needed to add more production, that it was too slow,” continues Cabello, before absent-mindedly pouring coffee on her grey cashmere jumper and earnestly imploring me for laundry advice. We dab her sleeve with water as Cabello tries out my accent. “I’ll have a flaaat whiiite,” she drawls, mischievously, again and again until I steer her back to the story. Persuaded that Havana would never get radio play, Cabello released Crying in the Club as her first solo single instead. But when the album was released, it was Havana that listeners pounced on.

A romantic: Cabello credit: WireImage

“It was surreal: kids were coming up to me asking, ‘Are you Havana?’” she says. The song was nominated for two awards at the Grammys, where Cabello became the first female Latin artist to open the ceremony.

Cabello’s grip on the charts is part of what Gold calls “a ground shift”. “Latin artists have gained enormous global acceptance in the pop world in the last few years,” he says. Until 2017, a Spanish-language number one was vanishingly rare, limited to Enrique Iglesias, Shakira and novelties such as The Macarena. That changed when Luis Fonsi and Daddy Yankee’s 2017 Despacito, written entirely in Spanish, became the most-streamed song in history.

That same year, the number of Spanish-language songs in Billboard’s Hot 100 jumped from three to 19; this year’s tally is already at 16. Such is the influence of Latin culture on current pop that Madonna’s Madame X album single Medellin, released in April, featured Colombian reggaeton star Maluma, and breakout Spanish star Rosalia’s modern spin on old-school flamenco graced the John Peel stage this year at Glastonbury. In between, of course, came the juggernaut of Havana.

Cowell says he never really thought about Cabello’s Latin roots when he met her. “And then of course it occurred to me years later, that she was turning things around.” He has since had success with another Latino group, CNCO. “So maybe I owe a lot to her.”

Even singers of non-Spanish heritage are now cashing in on the genre, as Justin Bieber proved with his hugely popular remix of Despacito. “It’s definitely annoying when people take things, but sometimes I’m inspired by things that aren’t necessarily my culture,” says Cabello. “I think with globalisation, genre doesn’t exist any more. It was surreal hearing people sing the chorus to Havana. So many young people had never even heard of the place.”

Cabello donated the proceeds from the song’s music video to support young, undocumented immigrants known as DREAMers – those who entered the US as minors and are seeking resident status. Her YouTube channel has been inundated with messages from Latino fans thanking her for making them feel more welcome in America. Cabello suffers from anxiety and tends to steer clear of social media but when I mention the messages she clasps her face with both hands and her eyebrows shoot up under her curly fringe. “Really? That makes me so happy. That’s why I want to tell my story, because when I saw pictures of what’s happening at the border, my heart was broken. That’s my story too.”

Cabello was six years old when her mother, an architect, carried her across the Mexican border, telling her daughter that they were going to Disneyland. “I have this one memory of my mother taking me into a gas station, but that’s it,” she says. They were detained for 22 hours before being allowed to proceed to Miami. Her father, originally from Mexico City, joined them illegally a year later after swimming across the Rio Grande. “I didn’t know what was happening,” Cabello tells me. “I just had a Disney calendar and I crossed off every day until he arrived.

“It’s why my mum loves that film, Life Is Beautiful,” she says, referring to Roberto Benigni’s Oscar-winning comedy about a Jewish father and son taken to a concentration camp during the Holocaust. “Obviously I’m not comparing my story to that in terms of, you know… but it’s the same idea of a parent pretending it’s a game to protect their child.”

Cabello’s as new album Romance, out today, is a tribute to first love. “Minute by minute storytelling”​, she says. “Like, we got in a fight last night, and this is the song I wrote the next day.” She describes the experience in terms of the 2001 film Amélie, which she watched for the first time last year. “Before, I was Amélie,” she says, comparing herself to the film’s titular dreamer, played by Audrey Tautou. “I was just living in my own imagination. I didn’t go out and meet people. I didn’t really make any friends. Amélie’s thrills are the smallest things, like being looked at.”

As a child, she hated attention so much that she would cry when people sang Happy Birthday to her. Her X Factor audition was the first time she had sung in public, and helped her realise she could transform on stage. “Now I’m like Amélie at the end of the film, when she falls in love for the first time and breaks out of her shell.” Cabello tells me she is finally in a good place with her anxiety and OCD, which used to manifest itself in rituals including hugging loved ones for no less than five seconds for fear they would die if she didn't.

Of the 72 songs Cabello wrote for the album, only a small number appear, each one dealing with the minutiae of relationships. Keen for me to hear some, Cabello summons her mother Sinuhe, who travels with her daughter everywhere and arrives at the café with an iPhone on which she plays me two new songs. One, Shameless, is a heavy, gothic ballad reminiscent of vintage Avril Lavigne; the other, Liar, a Latino song carried by a powerful brass section that makes you want to get up and salsa.

As with her last album, Cabello has a writing credit on every track of the new one – a rarity in an era when so many hits are manufactured by teams of writers and producers. Is she making a statement?

“No, but I need to tell my own stories,” she says. “I still regret my first single, Crying in the Club, because I didn’t write it and it didn’t feel like me. I had the chorus to Havana, but I went with what was safe, what industry people said had worked before. Turns out, no one has a clue.”

When Cabello uses the word “industry”, her expression, usually warm and trusting, becomes uneasy. The absence of freedom she experienced early in her career as part of a label-curated girl group appears to have bred a distrust of the system.

Part of the machine: Cabello in Fifth Harmony credit: Getty Images Contributor

“Fifth Harmony was like its own separate person. It’s like we were serving Fifth Harmony,” she says, tugging on the sleeves of her grey cashmere cardigan. After Cabello left the group in 2016, she was accused of betrayal, and things got nasty – when the four remaining members opened the MTV Video Music Awards in 2017, an elevated platform showed the silhouettes of five women, until one was unceremoniously shoved off the stage as the performance began. “It’s so normal for groups to disintegrate. I think it has to be some miracle for five people to stay together,” she says. "I’m so interested to see what makes it different for Little Mix [and X Factor girl group still going strong since they formed in 2011]”.

In 2020, Cabello will make her next career move – into acting. James Corden personally picked her to star in and contribute to the score of a modern musical version of Cinderella, which he is producing. “He saw my L’Oreal advert where I was basically just being an idiot, and he thought that was cool,” she explains. She sounds a little daunted – and is currently taking acting classes – but it feels like the obvious next chapter in a life that is taking on a fairy-tale dimension of its own.

“You know what,” Cowell had told me before hanging up. “I would never have guessed, all those years ago, that when I met someone who was having the worst day of her life, who was crying at the back of that arena, that now we’d be having this conversation. Can you believe it?”

Camila Cabello’s new album Romance is out now