The Genius Heir's Vengeance

Quinn Hall wants to finish school and graduate. She is the Hall family's biological daughter and won a gold medal at the International Mathematical Olympiad, but her parents, her brother and Avery, the girl raised in her place, framed her and had her sent to juvenile detention. Three years there produced a second personality, Raine, who is willing to destroy anything, and the only thing that settles her is a music box left by the foster mother who died. Quinn comes back quietly and says nothing about any of it. Avery will not let it rest. She burns Quinn's books, ruins her medication, and finally breaks the music box. The Halls do not understand what they have let out.