Hermione hadn't wanted the kiss to end. Moving her hand to her mouth was a way of trying to hold the kiss there when Ginny retreated. The little taste had been like a Fortescue's new flavor sample. It left Hermione wanting more.
When Ginny asked if she was alright she lowered her hand and gave a simple nod. Her hand made it's way to lay on the one Ginny had placed on her knee. "I'm fine," she gave the other girl's had a little squeeze. Suddenly she wished that the kiss hadn't been just a demonstration. "Thank-you," she added flicking her tongue quickly over her lips.