Mdd, yes, there are limits; check them out. You can start with the famous story Rabbi Pliskin relates of the worker whose boss wouldn’t pay him.
Judging someone is rarely an obligation. Most times, we can interact with people and not judge them. Rare is the occasion when it is not meritorious to judge them l’kaf zechus. A BY girl who is wearing a short skirt does not fall under that category. You approach the person in his or her totality – the bein adam lachavero, the davening (trust me, these girls can and do daven quite seriously) and much more that you don’t have a clue about from a casual interaction. Hold on to the good thoughts.
Just a thought this erev Yom Kippur, from someone who’s going to be judged…