Buffy has the hilarious image of rubbing the blood on the tree and the two of them jumping behind a bush, kind of like in some wacky cartoon, and she had to bit her lip to keep from smiling. It was funny actually. "Alright. I'll smear the blood, you go get a head start on the running."
The blond put the blade to her upper arm and sliced quickly, barely wincing as it cut her skin and a thin sliver of blood formed on the skin. Walking over to the nearest tree, she dabbed a bit of it on the bark.