Dominique is Dead (1979)

There's spooky stuff going on in their mansion and Dominique believes her husband David is trying to drive her insane. After her death, David starts wondering if he's going mad himself as he keeps seeing Dominique in the house and outside his office. The twist ending answers the question of whether Dominique is truly dead and whether the supernatural inhabits the home. Not a particularly original film, it's similar to Gaslight and countless other driving the spouse insane plots.