Sexy Sisters (1977)

Plot

Edna has sinister plans for her younger sister Millie, whom she keeps drugged and confined to her bed. Millie’s newfound nymphomania only fuels Edna’s twisted desires, as she orchestrates a parade of men to appease her sister. However, Edna's true motive revolves around their parents' fortune, which will go to Millie on her 21st birthday. If Edna can convince others of Millie's insanity, the money will be hers. When one of Millie’s suitors opens the door to the outside world, the sisters find themselves in a battle against Edna's malevolent schemes.