Visual clue ?
Saw this melodramatic nonsense last night and since it was at someone else's house I couldn't stop/pause the DVD, but I'm pretty sure that in the first scene where "Alice" is looking for the keys in a chest of drawers, as she opens the drawers there is a book on top of the piece of furniture with a title like "The (something) Sister".
Maybe somebody with the DVD could freeze frame and let us know.
PS: Heather seems somewhat better endowed here, did she have a boob job?