Severus closed his mouth with a small cough and shook his head. "Sorry -- I, ah, didn't mean to stare," he said, returning her smile.
He'd never really had a study date before, apart from with Lily, though their study sessions had usually been nothing more than a thinly veiled excuse to chat. So, because of that, he wasn't quite certain of the protocol. Should they make a bit of small talk before getting down to business, as it were? He'd rather missed the opportunity to say hello, since she'd caught him gawping at her, so instead, he cleared his throat a bit awkwardly and asked, "How are you?"