Since you are her customer, all her niceness has to be deconvoluted. All the niceness that may or may not be added by her being a paid service person, you have to remove somehow.

I assume you 'meaningful' in 'romantically meaningful'. Then it's probably not.

Maybe she just goes to talk to you when she is bored/there are fewer customers/her collegue she liked to chat with in the kitchen isn't there. Maybe all it is is that you are there often, alone, a paying customer, and she liked to be friendly to you, just because.
We are similar, in a sense, and I sometimes feel completely 'naked' and feel like people are nice to me because they realize what I am deep inside, and they feel sorry for me. But I feel that's paranoid thinking and people are nice to you, and probably to you, because they feel like, because it makes them feel better.

Unlike you, I would never wear a shirt like that. It's kind of an invitation to 'extroverts' to come to talk to you, right?

She did ask you questions, which is a good sign. But it doesn't seem you two connected on that subject. I don't know what exactly was said and what the body language was, so maybe you did well. Maybe you did horrible. Hard to say. Anyway, you usually want to let her do most of the talking, asking her questions, but without it sounding like an interrogation. You ask a question, you comment on her answer, repeat. Then, hopefully you can say some funny, witty, interesting things that impress her, make her laugh, and make her notice you are really listening.

Whatever she doesn't know about you, she will fill in the blanks as she sees fit. If you feel you don't know her well enough to ask her out, she has less clear reasons to say 'no', if she is presupposed to going out with someone like you (be it customer/IT person/introvert/fill-in-whatever.

Say that in her mind, she would never date a 'socially inept' person. As long as she doesn't know you think you are, she may say 'yes' where she would have said 'no' if she knew y ou better.
Same with you being a chatty customer with her for 6 months, 1 year, only then ask her out. Maybe you weren't single, or something. But you not escalating stuff means something to her. In a sense, you can make up who you are as she doesn't know who you were in the past or how you and others view you. I hope you get what I am saying. I am not saying you have to ask her out the very next time. I am saying that if you think your interaction should belong on a romantic trajectory, you should nudge it that way, somehow, and make your intentions clear.

You have to be bold somehow, and have it appear natural, and not preplanned. You have to meet her when there is no service person-customer relationhip.
I know how hard it is because I am in a similar situation and the clock is ticking. It has to be me and her. It has to come up somehow. Then I can bring it up.
Same with her. She may quit her job at any moment and you will never see or talk to her again. You don't know.

Best if some shared interest comes up and you propose you can turn that into an activity and if that goes well you can propose something clearly romantic.

Anyway, it is not clear from this post and I don't remember you telling. What do you want? What is your ideal fantasy with her anyway? I assume it is romantic, but that's not explicitly stated. And what kind of romantic relationship is also of relevance.

Just my meanderings. What do I know. I assume the people that make the bold move do make a fool out of themselves, act awkward, but the other person just likes them so much, they say 'yes' anyway.