Greg realizes as he sits by Rachel's bedside that the thought of her physically dying didn't emotionally register until he couldn't talk to her again.
I really wanted Rachel to wake up. In retrospect, this was stupid and pointless, because I had nothing to say to her, but I just wanted to talk to her again.
Also this:
This was a human being, dying. This was the only time there was going to be someone with those eyes and those ears and that way of breathing through her mouth and that way of building up right before a monster laugh with her eyebrows all raised and nostrils flaring a little bit, this was the only time there was ever going to be that person, living in the world, and now that was almost over, and I couldn't deal with it.
From the movie
Rachel's death scene is turned up to eleven in the film, as opposed to simply dying ten hours after Greg's last visit. Here's how: on prom night, Greg shows up at the hospital with the film he and Earl had made so he and Rachel and watch it together. They're having a good time and Rachel's clearly moved ... then her eyes start bugging, and it's immediately obvious that she can't breathe. It's so bad that she can't even tell Greg she's choking.
Greg's reaction just makes it so much worse. While the doctor tries to help her, Greg can only look on helplessly before they usher him out. And when the door closes, he finally cracks, sliding down against the wall before he just sits there and starts to sob.
Despite everything happening to her in that moment, Rachel keeps her eyes on the movie playing in front of her, determined to finish it.
Greg: That was the last time I saw Rachel. She went into a coma shortly after that, and died about ten hours later. I know I told you she doesn't die, and I'm sorry. Deep down, somehow, I didn't think she would. But she did.
