Malamour (1970)

Louison, 14 years old, observes the adult world with skepticism but envy. During a family weekend at the seaside, she begins to suspect Pierrick, her sister Emma's boyfriend, of Misaffection. Spying on the young couple, she gradually discovers the physical and psychological violence Emma is subjected to. She then tries to free her from Pierrick's grip, the seemingly perfect lover...​