I remember this film - think it was a made for tv movie - don't think they were twins though - but one was good and one was bad - I relly liked the film when I was young - it freaked me out - the good one was in the car and could have helped the bad one undo the seat belt - and that's why she came back to haunt her. The freaky bit I remember was the good one telling her parents the sister was there and they thought she was nuts and when they left the room the bad one rolled out from under her bed. The good one ended up at the end of the film in a straight jacket locked up in the loony bin - can'r remember the name of it though - think it might have been part of the Hammer House of Horror films that were shown early eighties - they were weekly scary film/stories that lasted about an hour to an hour and a half