Doppelganger (1993 film)

Doppelganger also known as Doppelganger The Evil Within is a 1993 American supernatural thriller film starring Drew Barrymore.

Patrick the writer soon starts to realize something is odd about Holly. As he spends more and more time with her, things heat up and he falls for her. Not knowing that she is as crazy as her brother Fred, who is in a psychiatric hospital after killing his own father. And when Patrick finds out that Hollys mother was murdered and she was the prime suspect, he starts doubting her sanity. But by that time he is too attached to her and does not want her going to jail. So when her brother Fred is attacked and she once more is a suspect he decides he is going to get to the bottom of it no matter what.

Source: Wikipedia