Behind the Scenes at Z100's Jingle Ball 2012!
The "Want U Back" singer wore winter white for her performance at Z100's annual holiday-themed concert, where she reunited with her X Factor pals One Direction. Backstage at the event, she opened up to Us about how fame has affected her life. "I feel like I've changed a lot and I have tougher skin," she said. "I've realized I'm very lucky."