As I watched this I did start doubting whether the events described by the protagonist was real or a strange psychotic episode. It had me going for a while although I think the story did stall slightly halfway as I wanted to get to the crux of why. Ultimately any confusion or doubt about what was happening was instantly answered in the last 5 minutes, which did make me feel deflated at the end as the impact of the movie could have been better if some of the mystery was left unsolved. Ultimately, poor Sarah did remember the actual events of killing her married lover along with herself and the initial back story given to us was false. Fortunately or unfortunately for her she survived the apparent suicide and is now in a coma trapped in her own mind, which boils down to the entire movie based on her mind's machinations of dealing with what happened during her comatose state.
The clues were there though, the water leak theme everytime she locked herself in a room (mapped to real world happenings as water drips from the ceiling onto her toe during her coma), the coma hospital guy no doubt a complete sleaze bag as she lies there helpless manifests in her coma dreams as the guy suffocating her, and of course the sleep doctor who cares for her is the lover calling it off before his untimely death by her hand. Very neat little bow to tie everything up, nowhere near as good as Memento or other movies of its ilk but not a terrible movie either I've seen much worse. All in all decent enough to watch on Netflix with a cup of tea in hand, even with the average acting.