Hermione hadn't thought he'd try, after he hadn't when she'd thought of it before, so she tensed, surprised, when he did kiss her - but he seemed... confident. It was such a change that she found herself swaying against him, letting him kiss her for just a moment - and then beginning to kiss him back.
She wasn't an expert at this. Reading didn't really prepare you for the practical application of some things, and it had been a very long time since he'd kissed her before... But she closed her eyes, moved her mouth against his. She thought he was actually very good at this. Good enough to follow his lead, at least.