Buffy took that as an affirmation that they both wanted to continue in this vein of wow-inducing activities and therefore spending time together/seeing each other, and was a little scared to attach anything more formal to it, in case that wasn't what Kirk meant, even if she knew she liked him a lot, and wasn't interested in anyone else.

"I'm glad." She said, brushing her thumb across the back of his hand and leaning in to kiss him again, briefly. Briefly only because of the aforementioned concern. "I should probably get back." She sighed, reluctantly. "It's either that or the joys of the Inquisition."