The Spider Woman Strikes Back (1946)

Jean takes the job of caretaker/companion (before the word took on a completely alternate-life style meaning) to blind woman Zenobia. Also hanging around the house, in this horror/western, is Mario, a deaf-mute servant who evidently wasn't much help to Zenobia when it came to identifying the source of a noise Zenobia couldn't see. Jean is a little slow in realizing that Zenobia is slowly killing her by taking her blood. Nothing personal. Zenobia needs her blood to feed some plants. She uses the blossoms of the plants to make poison to kill cattle in order to drive away the local ranchers so she can buy all the land...cheap.