"Aaaahhhh," said Billy -- and it really was "saying" it, as opposed to a scream. It was a thing he did when he wasn't sure what else to do.
It took some scrambling, but he managed to scoot completely off of her, and crab walk backward until he was far enough away to be out of her personal bubble.
"Jesus fuck," said Billy, and it was probably not the best greeting he could have gone for.