Hi, c30. A lot of times after a first date, if a girl is really sweet and kind of innocent (which is VERY hard to find these days), she may have several feelings, like a little shyness; maybe embarrassment; maybe wondering what you think of her; wondering if you thought you liked the way she kissed; maybe wondering if you're going to want to see her again...(all kinds of things run through our minds. I agree about just talking to her. By no means leave her alone. That would be the worst thing you could do. I mean don't be all up in her face, but you could tell her how much you enjoyed ing with her, etc. And, depending on how the conversation goes (like if she starts warming up to you), you could even thank her for giving you such a sweet kiss.
Some behaviors exhibited by ladies after such a moment might strike you as odd, but they are normal to them. Perhaps she is waiting for you to make some kind of follow-up, but it would be best if you talked to her for firsthand information.