He'd never know how much she needed to hear that. Everyone had been telling her, over and over again, that this was the man he'd become. That, before long, the one she knew and trusted with her life would turn into the one standing before her. She'd wished so desperately that she could be angry about that. That she could just turn her back on him when the time came and not go off with this relative stranger. But she couldn't. And it was more than the fact that he was physically attractive. Which she couldn't deny. There was a reason Rose hadn't stepped away, though her hand dropped slowly to her side.
But she wanted to believe in him. She wanted to believe that this person she'd allowed so close to her was the one who was going to take care of her. Maybe he wasn't her leather-clad friend, but he also sort of was, after all. And he'd been so good to her before she'd found out the truth. Offering her comfort when it was needed, boosting her confidence when she was obviously not feeling it on her own. If that was what this regeneration thing would do to him, could she really fight that?
"I still don't understand why," Rose admitted quietly. "Why me? Hell, why ask me along in the first place? Don't get me wrong, I wouldn't change a day of it. I just... I'm just me, that's all. And you seem to have so much faith in me..." And, as anyone who knew her well knew, Rose Tyler had so very little faith in herself sometimes. But not with him. No, as fabricated as he might have been, John Smith had offered her up plenty of confidence. And so did the Doctor. Really, it was a wonder she hadn't put two and two together days earlier.