Emma, puertas oscuras (1974)

Teenage girl Emma (Susanna East) is involved in a car accident and suffers a serious mental condition. Against the doctors wishes her mother decides to lock her up and care for her at home but her behavior gets worse by every day until she loses all control and begins a murderous rampage.

Spanish cinema at its finest, José Ramón Larraz delivers a gritty shocking psycho slasher tale of a teenage girl gone bad, really bad. This is some obscure, rare stuff that is definitely  worth a watch.