Melinda begins her school year as a rape victim who has been humiliated and shamed by her friends for calling the police after her rape, which results in the party that all the kids were at being broken up. With no one knowing that she was raped at the party, she is ostracized, unpopular, and shamed into silence. She retreats into the janitor's closet and tries her best to be invisible.
Her growth and recovery begins with her art teacher, Mr. Freeman, taking an interest in her and her art. Being befriended by her lab partner, David Petrakis, also aids in Melinda's recovery.
I would argue that a big part of Melinda's recovery comes from being forced out of her comfort zone by the realization that her rapist, Andy Evans, begins dating Rachel, who is Melinda's former best friend. Having been mute for most of the school year, Melinda needs to find her voice (albeit in the form of notes exchanged in the library) to warn Rachel about what Andy is really like. After initially reacting in anger to Melinda's accusation, Rachel soon comes around and winds up publicly dumping Andy at the prom.
By the time Andy gets Melinda alone in the janitor's closet and attempts to rape her a second time, she has found her voice and screams loudly enough that the lacrosse team comes to her rescue.