I like the waitress at the coffee house I go to. Could she like me at all?

Ok so there's this waitress at the local coffee house, i'm 22 and she's 19 y.o. I see her almost every time I go there and ever since I asked her for her name she's very friendly with me, she always greets me with a smile and asks me how I'm doing. I'm always very polite with her and I'm pretty sure there has been some flirting between us. For example once I was with a friend of mine and as we were leaving the coffee house I held the door for her and smiled and she smiled back. Or the other day, I was on my way to the bathroom when I noticed her trying to adjust the knobs on the DJ console, she seemed at a loss, so I went up to her and teased her a bit and she seemed to enjoy it, she laughed quite a lot. And of course there has been a fair share of eye contact, I've locked eyes with her a couple of times and I've noticed her looking at me from some distance. But the strangest thing happened about a week ago. I was out with a female friend, having a walk, when I spotted a girl some way ahead looking at me. She was waiting to cross the road and I couldn't see very well who it was. When I came closer and she saw I was with a gf she turned away and stopped looking, and the next day when I saw her at the cafe she was acting kind of strange, like she was trying to look super-cool and easygoing. Maybe it's my idea but I'm pretty sure she would have at least said "hi" if I wasn't with female company. So the thing is I really like this girl, I think she's really sweet and a nice person, not to mention that I find her very attractive. Could there be any chance that she likes me and she's not being just polite because I'm a regular customer? And is so what do I do? Should I flirt a little more directly (more eye contact etc.), should I ask her out for a coffee? Thanks a lot for reading this and for your help :)