Why She's Hot: Far removed from the personal problems that threatened her career two years ago, Demi Lovato has used thesupport of her fans and some ubiquitous pop tunes to triumphantly rebound to the upper reaches of our 21 Under 21 list. The former Disney star's 2011 album "Unbroken" yielded her first Top 10 hit on the Hot 100, "Skyscraper," but follow-up single "Give Your Heart a Break" was even more of a hit and has spent nearly half a year on the chart. Meanwhile, Lovato scored a prime TV gig by joining the U.S. "X Factor," where she can judge other aspiring vocalists alongside Simon Cowell, L.A. Reid and another pop princess, Britney Spears. Throw in an acclaimed summer tour with Hot Chelle Rae and a hosting gig at the Teen Choice Awards, and this year was one in which Lovato made the leap into the upper echelon of pop personalities.
Video Below: Demi Lovato's "Give Your Heart A Break"