That puts his lower half out of her reach, but she lets it go for now. He'd given her the impression that he was basically human-shaped, and she believes him - but he is an alien, and she can't help but feel a twinge of worry that she'll pull down his pants and find something completely unexpected. Taking it just a little more slowly than usual is all right with her.

She knots her fingers back into his hair, and gets to work shimmying out of her underpants.