What a nice guy. She couldn't get any blood outta him, so he hurt himself in order to draw blood just to let her taste it.
Also blood makes vampires horny? Sounds great. May as well give her some sperm while you let her have your blood.
Great ending though. Well hey, she gets blood and sperm, and we get some sweet monster girl Vanilla. Nice.
And she may as well come visit him on a regular basis, or rather, she may as well move in with him.