It's a surprise to her too, though a welcome surprise.

To be honest, his ability to surprise her is one of Luna's favorite things about Draco. She lets out another small sigh, eyes drifting shut for a moment. If he weren't so uptight, she would have so many questions for him, about what he likes and how things feel for him and-- well, a great many things.

Instead, she deliberately brushes her knee up his thigh.