Originally Posted by CarScar
... What makes you think that? He could have left right after Lee got in it, but he waited for Lilly to get down the stairs, he even backed up towards her. If he attempted to leave Lilly behind I'm sure someone would have mentioned it.
The only thing about him leaving Lilly is when he speaks the line "Screw her, let her stay!" when Lee is yelling at her to get on the RV. I don't think he meant that as a desire to leave her intentionally, more as a way of saying if she won't come down to the RV then she can stay behind.