I'm close to losing this girl? Quite long.?

Right so I really like this girl and it's not down to looks, I realized there were plenty of fish in the sea so if a girl didn't take interest in me it was easy for me to move on, but we have this sort of chemistry and it's down to the way I treat her, because I treat her as a friend not a potential gf, this is because she's a bit of a tom boy well more than a bit, but I really like her . But I have lacked confidence in my new college because none of my friends are in the same class as me but now there is a friend that is joining this college and he is in the same class as me, also there not many boys in fact there's 2 boys and a lot more girls. Thing is she did have a bf but she still kinda of flirted with me still by looking at me quite often, teasing me, fidgeting and she talks tries to talk to me quite often but like I said I lacked confidence also I was not planning a move while she had a bf, but now I found out there not together well 3 days ago but they split up weeks ago and she has stated this boy is after her but she is not sure but like I said a friend of mine is joining and might give me a confidence boost to actually move but I don't know what to say and how I should be judging this situation but I can't keep her off my mind and I just want her to know the real confident me.