As a guy, we should limit our range with another girl that's not belong to you (your girlfriend). It happens to me last time, it almost causes breakup. Things could be simply said like "She's just my friend!" But, i only treat her as my friend but what bout her? I know she likes me & she know i have girlfriend, but she wouldn't mind. Things didnt says out but we "should" / "will" feel something is "telling you" she is not only just an ordinary friend.

Quarell with my gf many times, in the end, i chose to ignore & my studies over, lost contact with the girl. Now im happily together with my GF.

So, control your "proximately range".