Better horror if she finds out she is #4
As we see in the movie, Lawrence plays her usual nagging self.
What if he tried this with 3 other girls before, possibly hot instead, but it never worked so he got rid of each one?
So she gives him all this shit about waking her up, till she realizes he is a serial dater and her only choice is to make him happy. Or exit through the garbage disposal.
Or kill him in his sleep, and wake a hot guy for herself!