La Petite Du Diable (The Killer Nun) – 1979

La Petite Du Diable (The Killer Nun) 
Sister Gertrude worked in a hospital, where she is appreciated by both patients and staff and her sister (Sister Mathieu). But ever since it was discovered she has a brain tumor, Sister Gertrude’s behavior is increasingly particular. Thus, headaches, delusions and desires of the murders take while working. Worse, she became addicted to morphine, and she now injects it insidiously to nightmarish trips in her subconscious….

http://www.horreur.net/film/la-petite-soeur-du-diable-2536