Hey, well done! I definitely see this as a cover on a book or on a movie. If I ever write a vampire book, I'll ask you.
I like the blue and white colors and the pale color tone, it creats an atmosphere which is what I like best in this photography.
Her mouth is scary, the open mouth and the teeth and all, but her eyes seems so helpless and there is lots of fear in them which creates both fear and compassion at the same time. This is a quite interesting combination of two quite different feelings, which makes the photo more interesting than it would be if there were only one of these.
Her hands on her chest makes the title more interesting, because it makes me thing that this could be a warning to all vampires: Watch up, or you'll get stabbed! (That's what I get out of it, you migh also mean "watch up for the vampires!")
I think it would be a good thing if both or neather of her eyes had make-up on them. Personally I would prefer neather, because that would look more realistic and also more original.