Rachel was actually reading the script of Friends when she was pretending to be reading Days of Our Lives.
In episode 19 of season 9, Joey asks Rachel to help him learn his lines for his role in Days of Our Lives, and she reads the lines for him. But, in fact, she was holding the script for that very episode of Friends. If you pause the episode, you can read the words, “The One with Rachel’s Dream.”
that is because it was an experimental cure for insomnia