"I noticed," she said before she could stop herself. To make it seem like she meant it pleasantly, she gave him a small smile and allowed herself to relax a little. He wasn't going to attack her so far as she could tell, and she was keeping a close eye on him to be sure of any change in body language. It wouldn't do to be surprised.
"Oh." She hadn't expected him to be worried about her name. "Sadie," she said, smile widening a bit. She resisted the urge to arch her eyebrow at him as he spoke once more. "No. Of course not." She shook her head slightly as if to emphasize it. "I'm afraid I don't recall your name either. You are in Gryffindor, right?" She supposed she should be absolutely certain before she added the information to her list. Of course, she wasn't sure if he was the sort to discriminate based on house. If he was, she'd know the minute he figured out which house she was in.
For the moment, however, he seemed at least polite, which she could appreciate for what it was.