I am sorry to say no. I have this particular problem. It is my "act" to be friendly and approachable. And far too often people confuse this for flirting. Or rather I confuse flirting with being friendly and approachable. But there is always one good way to find out what the intent is... just "make a move". Just ask in a very laid back way if she would like to do something outside the regular interaction. It doesn't have to be major. For example say your going to Starbucks and would she like something ... or like to come with you. Even if she comes that doesn't mean she is into you but it probably will give her the heads up.. and if she backs off then, they you probably know what your dealing with.