My initial ideas for a horror film

My initial idea for a horror film would be a psychological theme combined with a paranormal theme. I would like the scenes to be located in an abandoned and scary building or room.

 I would like the horror film to include a character who is very popular and she meets a girl that is unpopular in a store room and she's never been seen or heard of her in school, she decides to become friends with the unpopular girl and she decides to introduce her new friend to her friends but every time she does the unpopular girl disappears and the popular girl's friends think she is going mad. Eventually we find out that the unpopular girl is a psycho and turns out to be the villain.