I am half way through the movie, maybe it goes really really downhill. But one thing I think a lot of the reviewers forgot about was a key detail. Cassie had a serious brain injury and was diagnosed bipolar. She stopped taking the medication. When she stopped doing that she became an unreliable narrator, the audience should not base her experiences in the realm of reality. She could be experiencing auditory hallucinations, delusions, etcetera, etcetera.
I would say it is a low budget horror win.