I don’t remember much as I watched this mo9vie a good 8-10 years ago.
I believe a woman who may be a psychiatrist (at a mental institute or jail?) comes home from work (which a jumpscare happens with a whimpering moving brown bag goes across the screen), her husband and sister great her on the couch. From there two of her patients (which turn out to be a rapist and his victim who might be dead? Unsure) break into her house and begin to torment them.
From what I can remember the little sister has a diary in which she writes how she loves her husband and teases him sexually when she isn’t around, and she has to announce this in front of everyone etc. The husband admits he finds her attractive all in front of his wife.
Anyhow, it turns out that she walked in on them doing the nasty on the couch and killed them flat out, she also killed her dog (the brown bag in the beginning). This caused her to have a mental breakdown, the last thing I can remember is her in the bathroom with blood all over her.
Honestly sorry for the lack of information, I cannot find this movie anywhere!