Movie about driving a woman crazy to gain inheritance

I saw this movie roughly 15 years ago, although it was in black and white. It's about a woman(call her Molly for now, though I doubt that was her name) who lives alone, until some relative(sister or cousin, I think) comes in. Throughout the movie, the relative is trying to convince the Molly that she's (Molly) is crazy. If I recall, the motive was to have her committed or something so she can gain some sort of inheritance. I vaguely remember one scene where Molly is in a room, and a decapitated head rolls across the floor. It may have been a skull, or full head, I can't remember. Thanks for any help.

EDIT

After some more discussion with the wife, we've come to the conclusion that the relative of "Molly" is a female, and that we THINK it takes place in a southern state.

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