Of Life and Limb — Tamara Hart Heiner

It's the end game that matters, and Cassie is losing fast. She's at odds with her best friend, struggling with her weight, and longing to be part of the in-crowd. School is quickly overwhelming her, and it's all she can do to keep on going.

When her crush encourages her to run for student council, Cassie thinks it might be just thing to revive her dying social life. And then she finds out she's running against her best friend. Suddenly it becomes an all out war.