''You know, I'm really just a normal girl.'' Leona Lewis repeats variations on this mantra often during an hour-long interview in the back of her black SUV, but all evidence points to the contrary. Consider the recent appearance on The Oprah Winfrey Show that catapulted her single ''Bleeding Love'' to the top of the Billboard Hot 100 songs chart. Or the debut of her album, Spirit, in her native U.K., which unloaded 375,000 copies in its first week to become the fastest-selling debut in British history. (So long, Arctic Monkeys.) Or this bon mot from Simon Cowell: ''Leona has the potential to be up there with Mariah Carey.'' Yeah, right. Totally normal.
Granted, Cowell has motivation to be effusive about this talented singer: He coached her to fame and a win on Britain's The X Factor, an American Idol-like talent show that has judges grooming the acts. ''I'm aware that when you make a statement like that, you've got to deliver,'' says Cowell, who co-produced Spirit along with music impresario Clive Davis. ''But I believe in all my heart that she really is that good.''
Fair enough. But over here in the States, we have expectations of our golden-throated divas a psychotic meltdown; a marriage to a much older, strange Svengali; or at least a tawdry reality show. However, Lewis, 23, isn't delivering any of that just the pure vocal goods. ''I'm naturally shy as a person. It takes me a while to come out with people,'' she says. ''I'm not loud and lairy, you know?''
Well, if Lewis isn't going to sell herself on the eve of her April 8 U.S. release of Spirit, we'll do it for her. Her four-month X Factor transformation into a power-note diva prompted Cowell and Davis to contemplate cutting her album together even before she took home the show's crown. ''I could just see the effect that she had on the audience,'' says Cowell. ''I thought, This girl's not just going to be big in England. This girl is going to be a hit all over the world.'' So far, so good. Her first U.K. single, a cover of Kelly Clarkson's ''A Moment Like This,'' bowed at No. 1 in December 2006. Spirit had its white-hot debut the following November, and it's since sold more than 2.5 million copies worldwide.
To be clear, Lewis has been preparing for pop stardom since she was pretty much a baby. Born in Hackney, a rather rough neighborhood in East London, she began singing, she says, ''literally before I could speak.'' She attended the prestigious Sylvia Young Theatre School starting at age 6. At 9, she began taking private voice lessons; soon after, she was singing at Wembley Arena. (''It was a song called 'Grocer Jack.' It's about a greengrocer and he passes away,'' she laughs, revealing just a hint of a maudlin side.) At 14, she enrolled in the arts-intensive BRIT School, where she began working in basic recording studios. By 17, she was cutting demos and playing gigs at local London clubs while working part-time jobs at a Pizza Hut and a mortgage brokerage. No, determination has not been a problem for Leona Lewis. ''She really impresses me,'' says Davis, who's presided over the careers of everyone from Bruce Springsteen to Alicia Keys. ''The major stars have that work ethic. They really have to work all year round, and they're willing to do it.''
NEXT PAGE: ''Thank God Leona loves being with her family,'' Cowell raves. ''I've had no demands, no weird requests for strange-colored water or cushions.''