Astoria had noticed Ron looking at her, not that she was entirely sure how to take it but it wasn't making her feel uncomfortable (yet) so it wasn't a bad thing. Though she was trying not to over-analyse things like she usually had a habit of doing, especially over something that wasn't a huge deal.
In any other situation Astoria may have found Ron's nervousness amusing, but right now it actually put her at ease and made her wonder why he seemed to be as nervous, as she was kind of oblivious to the fact that this was possibly a date. "Well, thank you for the offer."
Astoria smiled, although Ron had been the one to suggest drinks she honestly hadn't expected him to be buying her the drinks. "I'm all right without one, but thank you though. I've been here before with Daisy, so I can almost remember what's available," she replied. "But to answer your first question, I'll have a Virgin Grasshopper."