wake up-written on the fridge in blood?

Um, Emmett was thirsty after killing all those people, so he got a drink, then he touched her hair, not rocket science.

It wasn't written in blood. With bloody hands, Emmet brushed Mandy's hair behind her ear and rearranged the magnetic letters on the fridge to say "Wake up." At this point in the film, you're supposed to think that it's meant to scare Mandy -- that she narrowly escaped being killed.