Looking for a movie about a girl trying to find a missing girl

Hi! i’ve been looking for this movie a lot, this is what i remember

A girl moves into an apartments (probably she is going to college..) and she finds out that her room, once belonged to another girl who went missing, there are like four guys (a nerdy guy, a popular guy..) who befriend her and they talk about the girl who is missing, and so, and then the protagonist finds a hidden tape (or a laptop) and sees the four guys raping the girl, she confronts the guys and tries to find the missing girl, she even went to her house and finds out she has a sister with down syndrome, the nerdy guy is the one who is more close to the protagonist and tries to tell her that what she saw on the film it;s not what really happened, and even tries to find the girl, apparently the missing girl is actually evil, and she edited the film to look like they rape her, but in reality she accepted to have a foursome with them, however they are still trying to find her, and who kill her.

And what happened is that she was fighting with the popular guy over the film because she was going to blackmail him, and they were on the top of a building with.. sewers? and he push her, and she die because she fell, the protagonist tries to find her body in the sewers and she does find the body, but also like the evil spirit of her (i think she kills the popular guy.)

that’s all i remember and, it’s not the movie called The dorm.
Thank you so much in advance!!
im looking everywhere for this movie 🙁

i also remember the protagonist visits the missing girl house and talks with the mother and even gets into the missing girl room and finds a bracelet or something