"Are you sure you don't want me to stick around?" Sam certainly wasn't naive enough to believe that he'd be able to make Dean's reaction any less horrible when it came about, but he thought that maybe, if Claire wanted him to stay, that he'd at least be able to serve as some sort of reassurance that things were going to be fine. However, if she felt that this was something that she needed to do on her own, he would be completely and entirely for understanding and respecting her feelings on the matter. Sam just honestly didn't want this to go badly for either of them.
"I don't mind hanging around if you want me to," he offered, shoving his hands into his pockets. "Otherwise..." He shrugged a bit and shot Claire a serious sort of look. "All I can say is that you should be fine. Dean loves you. He'll understand."