Kate is world-weary due to her early-in-life parental abandonment and subsequent bouncing from foster home to foster home. The damage she has done to herself and others (such as her time in a gang) is revealed in flashbacks here and there when she considers where she's been - and where she's going. Her recent efforts to become a better student have also made her a better person. Her best friend Felicia and her social worker Tisha are very supportive, and her current foster parents are good people - even if Kate doesn't always see eye-to-eye with her foster mom.
Kate's summer story is a very good one, and I recommend it.