What does this mean?- relationship question?

I recently asked a girl out. She and I are friends, and I am usually sort of a date/escort to parties and such. But she said no and we just went back to normal for a while. That is until she started I guess you could call it flirting with me. I didn’t notice until one of my friends told me this, so now I am wondering a couple things: a) is she really flirting with me. B) if so why? Is it because she does want to go out with me or what?