My Double Life by Janette Rallison

Her whole life, Alexia Garcia has been told that she looks just like pop star Kari Kingsley, and one day when Alexia's photo filters through the Internet, she's offered a job to be Kari's double. This would seem like the opportunity of a lifetime, but Alexia's mother has always warned her against celebrities.
Rebelliously, Alexia flies off to L.A. and gets immersed in a celebrity life. Not only does she have to get used to getting anything she wants, she romances the hottest lead singer on the charts, and finds out that her own father is a singing legend. Through it all, Alexia must stay true to herself, which is hard to do when you are pretending to be somebody else!