Keeping the Moon by Sarah Dessen

Fifteen year old Colie has never fit in. First, it was because she was fat. Then, after she lost the weight, it was because of a reputation that she didn’t deserve. So when she’s sent to stay with her eccentric aunt Mira for the summer, Colie doesn’t expect too much. After all, why would anyone in Colby, North Carolina, want to bother with her when no one back home does? But Colby turns out to be a nice surprise for Colie. Almost without trying, she lands herself a job at the Last Chance Bar and Grill. There she meets fellow waitresses Morgan and Isabel- two best friends who teach her what friendship is all about and help her learn to appreciate who she really is.