Sex, Your Only Weapon (1981)

When Marta was a child, her father killed himself after his partner Humberto ruined their wine business. 20 years later, Marta pretends to be blind and befriends Humberto, who invites her to spend a few days with his family. She knows all the members of the clan and puts into practice the plan of revenge that she had devised since her father's death relegated her and her mother to poverty.