Does this girl like me? I'm kind of lost.?

So there's this cute girl who works at the front desk check in at my gym. I came in to workout one afternoon and she checked me in and asked "why do I keep coming so late lately" and while I was answering her, she was biting her lower lip, which was pretty sexy to me.

The next day or so this guy at the gym who I have been talking to, we had talked about that girl and he told me he was going to introduce us together, unexpectedly he did so and he brought me over to her, but she was on the phone plus her boss was there so it seemed she was pretty busy. We shook hands, I tried to flirt a little by asking where she was the other day because I had came early just for her. She told me she doesn't work that day because of school, and then she told me she would talk to me later..

I see her the next day, she checks me in and just says "thank you" and nothing after that.

So what I wanna know is, what are the signs this girl is trying to throw at me? Is she interested?