I agree with BooTheGhost that she was probably already dead but I don't agree with the coffin idea or anything else. I think she's dead and he doesn't know what to do, he hasn't gotten over her and he's sitting on her hospital bed thinking of her. He's trying to put himself in her shoes "My hair started growing, my face became yours,my femur was breaking in half. The sensation was scissors and too much to scream, so instead, I just started to laugh."
In his mind he's also watching as she leaves her ring behind and leaves, this symbolizes her departure from life and her anding their relationship.
I agree with BooTheGhost that she was probably already dead but I don't agree with the coffin idea or anything else. I think she's dead and he doesn't know what to do, he hasn't gotten over her and he's sitting on her hospital bed thinking of her. He's trying to put himself in her shoes "My hair started growing, my face became yours,my femur was breaking in half. The sensation was scissors and too much to scream, so instead, I just started to laugh." In his mind he's also watching as she leaves her ring behind and leaves, this symbolizes her departure from life and her anding their relationship.