NEW YORK - "You get the best of both worlds," Miley Cyrus sings in the theme song of her hugely popular Disney Channel show, "Hannah Montana." It's a reference to her character's secret double life as both a rock star AND a normal schoolgirl.Offscreen, though, this 15-year-old phenom is starting to learn how hard it really is to have the best of both worlds: as a G-rated Disney superstar AND a real-life, growing teenager with an eye on a long career.Cyrus, whose fresh, easy charm and down-home southern appeal have catapulted her to an astonishing level of celebrity, especially in the past year, found herself having to apologize Sunday for some entirely un-Miley photos in Vanity Fair magazine.At a moment when she otherwise would have been relishing an amazing week a deal for her memoirs (reportedly seven figures), the cover of People magazine and a feature in Vanity Fair she issued a statement saying how embarassed she was. This came almost certainly at the behest of worried executives at The Walt Disney Co., for whom she will reap a reported $1 billion this year.For the record, only Cyrus' back and shoulders are bare in the most controversial shot by Annie Leibovitz, the renowned celebrity photographer. Many an Oscar-night gown would show as much skin. Cyrus herself told the magazine in an accompanying article that she found the photo, in which she gathers a sheet around her, "really artsy. It wasn't in a skanky way. And you can't say no to Annie."But Cyrus IS 15, with a fan base that begins in preschool. And it's what the photo suggests rather than shows the idea that she might be nude, perhaps even in bed that bothered some parents who poured their feelings onto blogs over the weekend. She wan't nude during the shoot, nor in bed, but she does have a subtle come-hither expression.Leibovitz said Monday that she and Cyrus had discussed the photos beforehand, and Vanity Fair said "Miley's parents and/or minders were on the set all day ... everyone thought i...