What to do?approach her?

My problem is, i am in a sportsteam where i do running and other sports. For a while now everytime i was going i watched a beautiful girl that was occasionaly staring at me so did i. After a while i was ready to talk to her, and the time i was warming up she approached to me and talked to me first. So we got to know each other better. After a while she approached again and we started discussing and when the time came i complimented her(the wright moment). I finished and i left. The other day i came we said hi and all these but we didnt talk to much as i wasnt watching where she is. I saw her in the beggining and and in the finishing, where i went to take my things and she was staring at me. I dont know if its important(this day we didnt talk to much was also there one other girl from my group that we necessarily do together the training as we are in the same group). So my problem is that if this girl(that approached me) did it because she is social and likes to talk to many people or because she like me? And what to do? to make it further by asking sth like number or date? or is it in my mind? sorry for the bad english its not my born language. Thanks