Leona Lewis just turned her back on an invitation to sing for President Obama. The British pop star says she's just too busy. The singer was “thrilled” at being asked to perform, but “it clashed with her tight schedule,” the U.K. Daily Mirror quoted an unnamed source as saying. Lewis is in a Los Angeles recording studio laying down tracks for a new CD, and she doesn’t have the time to entertain the first family. Michelle Obama reportedly is a big Lewis fan and listens to her first album, “Spirit.” Could it be that we’re seeing some loyal royal payback?