She didn't want to take it back. That, despite it not really meaning much, meant the world to Castiel. It meant she didn't want to pretend it didn't happen, despite how she was acting right now. Knowing she was going to let that stay there between them, let him know that she loved him, that was something that proved it wasn't something she simply said, without the feeling behind the words. Castiel had known, without a shadow of a doubt that he really loved Meg, but hearing her say that, it confirmed his feelings were reciprocated and that was a first for him. For someone to take his feelings, accept them and then return that, it made sorting through emotions less confusing, although it hurt no less than being turned away, it seemed.
He followed behind, wordlessly and entered the room not but moments after she'd tugged the shirt from his closet over her head. He'd thought of offering her a shirt, not because he hadn't seen her body before or simply for decency's sake, but rather for comfort. He wanted her to be comfortable and he wasn't seeking out intimacy with her. Not that sort of intimacy, at least. He told her she would be able to rest and he meant that. He may have spent the past week without her, the whole of that missing her, but he also spent quite a few restless nights thanks to her disappearance.
"What do we do now?" He asked this, knowing that Meg was just as unfamiliar with emotions and humanity as he was, thanks to lacking in it for thousands of years, but he was uncertain of what she wanted. His feelings for her would remain, unchanging, but he also refused to trap her.