- Alternate Character Interpretation: Cassie was the book's real villain. She introduced Lia to the obsession that would destroy her body and ruin her adolescence, then blamed Lia for being the bad influence when Cassie herself slipped up enough to draw her parents' concern. Her very last words for Lia are far more haunting, and far more indicative of how much of a Poisonous Friend she was, than any of the things Lia's subconscious had spoken through the "ghost" Cassie's mouth.
- Angst Aversion: Lia is a very dark and depressing heroine and her struggle gets a lot worse before it gets better.
- Base-Breaking Character: Lia herself. Some find her a fantastic and complex character whose descent into self-destruction is clearly justified by her mental state, the struggle with anorexia and self-harm that's defined her adolescence, and the bombshell dropped on her at the start of the novel. Others find her a whiny, unsympathetic rich kid who created most of her own problems.
- Crosses the Line Twice: Elijah bailing on a mentally unstable Lia and leaving her alone in the same hotel Cassie killed herself? Dark, even though his intentions were good. Elijah casually mentioning that he'd stolen the cash she'd withdrawn for their great escape on his way out, save $20 for her cab fare? A little bit amusing. Even Lia doesn't seem to hold it against him.
- Draco in Leather Pants: Lia is very popular in some pro-anorexia circles. Not the Lia who realises how much she wants to live, gets better at the end, and begins the healing process, but the one who masterfully fools her way through rapid, unhealthy weight loss, meticulously controls her calorie intake to minimalise weight gain, and resourcefully tricks her family into thinking she's in recovery by tampering with the scales and inflating herself before weighing.
- It Was His Sled: Cassie's exact cause of death is a mystery to Lia for much of the book, but is so representative of the book's themes that it's mentioned casually in many synopses of the novel.
- Jerkass Woobie: Cassie has shades of this. She died alone, messily, and in considerable pain, futilely reaching out in her last hours to a friend she'd abandoned and blamed all her problems on. Lia and Elijah might also qualify.
- Memetic Mutation: Must. Not. Eat.Explanation
- Misaimed Fandom: A major one. Some pro-anorexia circles consider this book their bible, and glamorise Lia's struggle while conveniently leaving out the physical and emotional suffering this condition has brought her.
- Nausea Fuel: Doctor Marrigan's report on Cassie's death is nothing short of revolting. And entirely realistic.
- Nightmare Fuel: Lia's mental breakdown is not pretty.
- Chapter 40 is nothing but the phrase "Must. Not. Eat." repeated over and over, more than a hundred times.
- As the breakdown gets worse, Lia cuts herself so bad that she sends herself into a coma from blood loss. If that wasn't bed enough, her beloved stepsister Emma finds Lia like this, no doubt being scarred for life by what she saw.
- Signature Scene: Lia shredding herself into a bloody mess and sending herself into a coma right before sweet, innocent Emma stumbles across the scene and is scarred for life by the horror. As disturbing as that is to think about.
- Unintentionally Unsympathetic: Lia for some readers, given that she constantly lies to the people around her and resists their efforts to help her recover. Though this was possibly an Intended Audience Reaction, given that the main conflict of the book is her struggle against her own self-destructive impulses. It is notable that several other characters, most notably her parents and stepmother, openly call her out for her lying.
YMMV / Wintergirls