The Adult Fear in the premise: your daughter, formerly a cheerful A student, suddenly skips classes and becomes more withdrawn, and you can't figure out what's wrong. For most of the school year, you believe that she's being an Attention Whore and try to invoke Misery Builds Character, to no avail, and give her art supplies as a Christmas gift to make her feel better. Melinda's parents must've felt awful at the end of the book when they learn she sneaked out to a party with Rachel, got raped, and then had to go to the same school as her attacker.
Melinda's PTSD attack when David invites her to a post-game party. She's already freaking out because she fell asleep in her school closet, and David unknowingly makes it worse.
I'm trying to remember how we got on the ground and where the moon went and wham! shirt up, shorts down, and the ground smells wet and dark and NO!—I'm not really here, I'm definitely back at Rachel's, crimping my hair and gluing on fake nails, and he smells like beer and mean and he hurts me hurts me hurts me and gets up
and zips his jeans
Made even worse in the film, where you can hear Melinda's muffled screams and see her attempts to fight back as she hits at him as Andy is raping her...
The Bathroom Stall Graffiti scene revealing that Melinda was far from the first girl to be attacked and traumatized by Andy.
Andy attempting to rape Melinda again in the climax. This time, however, she's conscious and Andy makes no attempts to coax her into having his way with her. In the book, seeing Melinda having a mentally Big "NO!" moment as Andy begins assaulting her yet again breaks your heart.