The Woman is a Devil1949

A young woman, driven by her obsessive love for her cousin's husband, conspires to murder her cousin to clear the way for herself. However, after the crime, the husband falls in love with and marries a kind nurse who cared for him. Shattered and consumed by jealousy, the woman's hopes collapse and she seeks revenge by falsely reporting her lover to the police, accusing him of murdering his own wife.