Woman Goes Crazy and Tortures Man at Lake House

by Andrea
(Serbia)

I can't remember the name of the movie where a man and a woman goes to a lake house, and in the first 40 or so minutes of the movie everything is normal and it looks like nothing's gonna happen.

Suddenly a girl/woman starts acting very weird, and the rest of the movie is about her torturing the man (and sometimes herself).

I really need to remember the title of this movie! :)