What is this one recent movie?

OK, so I know it's less than 4 years old. I remember from the movie that the main character girl found her father and her house cleaner secretly having an affair and she got so mad that she burned down the house. Then, she got out of the mental institute and sees that the house cleaner was actually a serial killer who poses as a staff member of a family's house, changes her name each time, and butchers them. And so, she shares this discovery with her sister and in the end, her sister was holding a knife, and told the main character girl that the house cleaner was gone. However, it turns out two seconds later that she was holding the knife and when the police came in, her dad rushed up to her and told her that her sister died in the fire. Also, the "fake" name of the house cleaner turned out that it was the name of her roommate at the mental institute and that the main character girl turned out to be super psychopathic and got locked up in the same room.