Sandy Shore, the Much-adored (The Cassie Perkins Series) (Volume 5) 2nd edition

For ages 11-15 Cassie Perkins is sick and tired of being told she's self-centered. She's determined to prove it isn't true. Fortunately, she has the perfect plan: making over the class misfit, Sandy Shore. All it will take is a little makeup and a good diet, and Sandy's life will be all she could ever want it to be. But there's something Cassie doesn't know. Something that all the makeup and dieting in the world can't fix. And she's about to learn that helping people isn't always as easy as it seems.