I would say that when she asked when you worked was definitely an IOI. I would lay off on the emails unless there is a badass show or party that you want her to go to, a situation that itself is a DHV. Or just send a chatty email w/ out any invitation at all, something like 'you won't BELIEVE what just happened...' She may just be one of those people who never checks her email, big reason why I'd rather have the #.
No matter what though, make an insta-date and join her table when she comes back in for coffee. If you get fired, well it's just help to stop treading water and find a better job.

Get up and throw your apron in the bosses face, tell him "fuck your coffee" and take the girl by the hand and walk out. You'll be a legend to your coworkers, and the story will last a lifetime.
As far as gaming across the counter, use humor. Whatever they order; act like it's the grossest most bizarre shit you've ever heard of. Then tell them you like their individuality and/or sense of adventure. Escalating will probably be difficult in the narrow window of time, so you may have to wait a few visits and be on game each time a particular HB comes in before bridgeing/#closing. Just calibrate, some will be ready right away.
Good Luck, Hope this helps.