something i noticed, Nicole arrives at the hotel December 23 but on day 7 Irving says it's Christmas Eve. Time isn't moving the right way in the hotel. It's obvious they are trying to connect it to Stephen King's The Shining, where the hotel is a metaphor for Jack himself, his body, and losing his sanity. I think the same thing is happening here. The mold is also on the upper floors, i think a metaphor for the "brain" being the part that is diseased.

Nicole is having a mental breakdown returning to the place where she was abused and as the repressed memories try to return.

There is no Rachel Foster. Nicole was the victim. Her father groomed and raped her as a child. Her mother found out and immediately took Nicole away from him. The "death" was the child Nicole became pregnant with due to her father's abuse. Her mother forced her to have an abortion and consequently lost her faith in god. In college, Nicole marched AGAINST abortion, probably due to the trauma of being forced against her will to get one. She felt like a murderer for having the abortion, her religious mother probably raised her to believe it was murder.

she needed to create a new narrative in order to survive with the guilt, so Rachel Foster is created. the name "Foster" brings to mind "foster parents", or perhaps a delusion that Nicole has "fostered"

Irving may be a representation of the unborn child she never had? He calls himself an invisible witness to the love. He talks about Rachel reading him stories but maybe that was Nicole reading stories to her unborn child in the womb. The hidden bedroom is a child's room, not the room of a 16yr old girl. It's probably a metaphor for the unborn child's life that never happened & the things Nicole wanted to give the child but couldn't and then she repressed it after the abortion.

Nicole finds a bloody shirt in her mom's car trunk but a shirt isn't large enough to cover a 16yr old girls body. However, it would be large enough to wrap up a baby.

I found the lack of criticism towards Leonard's actions to be disturbing but perhaps it intended to show how victims become attached to their abusers, especially young ones who have been groomed? and if Irving is the unborn child, Nicole may have rationalized that he would have wanted his parents (Nicole and Leonard) to love each other.

in the end she can choose to live and continue in her delusion that everything will be okay, or die because she can't live with the truth she has remembered and realizing that she was the victim and the parents she loved were monsters.