Pretty sure it was in color; I think it was from the 1970s but might have been 60s or early 80s. There’s an adult woman who’s miserable because she’s living with her crazy mother in the mother’s house. At end of movie, the woman’s in the attic, and discovers a dead body that’s been hidden in the attic for years. Maybe her father? Can’t remember for sure.
The Attic (1980)?
Die! Die! My Darling(1965?