Hahaha she wants the D, bro! Even if she's joking, it's pretty cool that she feels comfortable enough around you to do that. That says a lot. Definitely a lot of "belly rubbing" potential there lol.
But in a situation like that, given a few circumstances, i'd be like "Girl, don't you tempt me!! I've got cold hands" and would've walked off laughing, and shaking my head.