Unfortunately that's not it....This movie is pretty old. Like early 80's old. I'll try and set the scene:
While her husband is downstairs with a beautiful woman-friend of theirs, she goes and takes a shower. But there is something else in the house watching them all through monitors/or something like that. During the shower, blood starts to come out of the shower head and she can't escape the shower because the glass shower doors won't open.
At my young age, this scene messed me up good, and I did not watch any more of the movie. Gave me nightmares and I would continuously check the shower doors to make sure they would open whenever I took a shower
Later on my father had told me another scene when the couple's mother came to visit and she was in a heated pool and the "thing" watching turned up the heat and pretty much boiled the lady to death in the pool.
This has stumped me for longer than I can remember.