I’ve been trying to find out the name of this movie for years. All I can remember is that it involved a rich pretty girl who was a psycho and killed people, but nobody realized this  at first. When she killed them she would completely wrap them in plastic and put them in the basement. I think it was a guy who had liked her who eventually discovered the bodies. I think the girl lived  near a lake or river because I recall a scene where she was in a metal fishing boat. The girl had dark hair. I saw this on TV sometime in the mid 80’s. I know this isn’t much to go on but it is all I can remember.   Thank you.