Camo Girl by Kekla Magoon
Before there was Ella and Bailey, there was Z, Ella, and Millie. The once inseparable trio has broken up. Millie is now popular, and has the equivalent of the time it takes the school bus to get to school to talk to Ella. Ella and Z are still friends, but Ella becomes more and more aware that Z's personality is getting a little weird for even her. Z escapes into fantasies more and more, and gets to the point where he never reaches for reality. But, Z is the only friend she has, that doesn't care about her color mottled skin, the only one who doesn't call her camo face. How can she turn her back on him?