The effects of Alienation- Melinda feels disconnected from all the groups she once felt naturally a part of. We see this mainly through her peer group and family. Her friends have not only abandoned her because of her apparent social gaffe at the summer party, but they have changed themselves into characters or molds to help fit into other groups.
The importance of Communication- Melinda doesn't share and this helps continue the alienation mentioned above. She has no connection with anyone and is not able to build any real relationships because of it. Look through the book and note her longest dialogue; there isn't much until the last fourth of the book. Her mom dominates one sided conversations at home, Heather from Ohio does the same as her "friend" and all of her teachers move forward without any real input from Melinda.
The effects of PTSD- Melinda has gone through a violent and traumatizing attack and suffers from post traumatic stress. When she is raped at the party, her life changes and she mentally and physically reacts to the stress. Physically, she eats for comfort and chews at her lips. Mentally, she shuts down and avoids opening herself up to more pain through relationships.
Climax- Reread the closet scene in the final section. Melinda gets attacked in her "safe space" of the abandoned closet, and she must use her voice and stand up for herself to stop from becoming the victim a second time.