[She starts giggling, yes, giggling, because his surprise and delight really are palpable and if there are some people looking, well, she's used to that, too. Ginny lets the glass dance around for a bit before she sets it back down, then gives her wand a twitch again and the last bit of beer comes swooping out of the glass, next.]

It's a wand, thank you very much. And it's possible to do magic without it, but not nearly as controlled, and I can only think of one wizard who could really do it. [Dumbledore.] We get our first wand at eleven years old.

[Now letting that blob of beer split into two and then four and so on, dancing around through the air.]

But we're born with magic. [This as she directs the beer back into the glass.] It's just how I am.