Perverse oltre le sbarre (1984)

The beautiful mixed-race woman Conchita steals a stash of diamonds from a criminal organization and hides it. While imprisoned, she makes use of her charisma, despite opposition from Helga and the tough warden. The organization tries to eliminate the traitor by sending a hitman into the prison, but without success. Conchita and Helga devise an escape plan, hiding inside two coffins supplied with oxygen masks. Conchita, who wants to recover the diamonds for herself alone, kills Helga. In turn, Rosy, their false friend, empties Conchita’s oxygen tank and steals the key to the diamonds’ hiding place. The mixed-race woman suffocates to death in the coffin.