You need to ask her soon before she thinks you're a stalker or a wierdo for coming in to her restaurant all the time.
So, the next time you go in, just ask her if she would like to get together sometime when she's not working.
Yeah, it will be awkward, so you should try to get her to serve you and then ask her when you are done with your meal.
There's no trick to this, you just need to make the words come out of your mouth.
Good luck!

Hey,
Sorry, I hadn't checked the site in a bit and missed your message.
Absolutley, you need to just come out and ask her. Take the risk, you may land flat on your face, or you may fly, you'll never know unless you jump in feet first.
You have Faith, right, well that is what it is really about. Trusting that things will be handled by a power greater than yourself. You have no control over her actions, but you over yours, so go ask her. Whatever her answer, it was meant to go that way.
Good luck