My old initial ideas before group discussions

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 in her 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 the popular girl finds out that there is something seriously wrong with the other girl and she finds out the unpopular girl is not really a human being. The popular girl tries to tell her friends but no one believes her.

Later girl finds out that there is something seriously wrong with the other girl and she finds out the unpopular girl is not really a human being. The popular girl tries to tell her friends but no one believes her.