Spoiler Alert. My take on it
Well my own opinion spoiler i suppose.
I think, now that I've seen it to the very very end, is that she is the ghost that the home owner was talking about. What makes me think so is that the guy she stabs never talked about the haunting, he described satanic rituals. Its as if he did know about any ghosts. Then at the very end, the home owner hires another young lady and starts saying the exact same lines as in the beginning. Now if the movie is supposed to be a loop of sorts, I don't think so, but it is possible.
But I certainly think that it was the satanic rituals that made her kill, she even admits it during the last phone call. What I didn't get for sure was what she saw in the room. But more than likely it was Old Scratch himself.
I think the movie was brilliant. The twisted eerie music really got to me. And Lauren A. Carter is wickedly beautiful and mesmerizing psychotic. I hate to make comparisons but I saw some of the young Christina Ricci with a touch of Reese Witherspoon in her. Her facial expressions were fantastic. They really drew the horror up close and personal. She is going to be one to watch.
This poster has been deleted by the message