"Die Sister, Die!" (1972) starring Jack Ging, Edith Atwater, Antoinette Bower is a psychological thriller with plenty of great atmosphere.
Amanda Price (Atwater) lives in a big old mansion in the remote foothills somewhere out west. Something from her past is haunting her and she keeps trying to kill herself - unsuccessfully. Edward (Ging) is her brother and he is tired of waiting for his sister to kill herself and he wants to help her along so he can finally inherit the family home.
Edward hires a former nurse with a past, Esther Harper (Bower) to "assist" his sister to a timely death. Esther moves into the mansion to care for Amanda and she slowly starts to learn about the mysteries of the Price family and learns she has signed up for something more than she bargained for.
I really enjoyed finding and watching this movie. The setting of the big old mansion in the hills was beautiful but when night came it turned eerie to match the sinister goings on in the house. This is one of those thrillers that will keep you guessing until the end.