Amma Crellin

Amma is the half-sister Camille barely knows, a teenager living a double life in Wind Gap: doted-on and childlike inside her mother's house, and a swaggering, dangerous queen bee the moment she's out the door with her friends, rollerblading through town like she owns it.

Eliza Scanlen plays the split without ever tipping her hand, so the sweetness and the menace feel equally sincere rather than a twist waiting to happen. The writing uses her as a mirror for Camille's own unresolved girlhood, and Scanlen makes that doubling feel eerie long before the plot explains why.