Orgasmo

Orgasmo is a 1969 giallo film co-written and directed by Umberto Lenzi and starring Carroll Baker, Lou Castel, and Colette Descombes. It follows a wealthy American socialite who finds herself preyed upon by two nefarious young siblings who indulge her with sex, drugs, and alcohol while she vacations at an Italian villa. This film helped launch the second phase of Baker's career, during which she became a regular star in Italian productions.

Synopsis from Wikipedia, CC BY-SA 4.0. Everything below written here.