Re: Umm yeah so this happened...
part of my first instinct is to reply with something like...
"too bad you never said to show it. (insert a winky face--i don't know which emocon it is)"
"didn't know i was a drive thru. but coming right up! that'll be 7 minutes in heaven please (insert winky face)"
ultimately i think you should be flirty about it. she's already kind of being flirty and forward. for sure you should acknowledge it. don't be push too hard until she uses much more... explicit wording--match her level of intensity. remember to always try to get her to emotionally respond. if you don't she's probably going to trail off into boredom a lot sooner. your goal is to meet up in person. once she responds to you acknowledging you should try to shift things to inviting her some place, some kind of meal at hers or yours and get things going from there.
Every moment counts, get out of your head and enjoy it.