You've got to toughen up. If she's waiting for you when you get home, tell her you don't have time to hang out and close the door on her. Tell her it's not appropriate that she keeps inviting herself over and that you can't be available for her on her whim. The only way to set boundaries is to set them strong and plain and then do what you have to do to enforce them. If that means walking in your door and shutting it in her face that's what you need to do.
She's not your kid, she's not a relative, she's not your responsibility. Tell yourself that when you feel yourself folding. She's pushing you because you're not drawing the line in concrete. It's not mean to set firm lines with people that take advantage of your good nature.
It's not appropriate to ask a woman out when she's working. Service staff get hit on all day and they're just trying to work.
You can slip her your number if she shows up at your place of business and leave the ball in her court though. If she doesn't contact you then there's your answer.