A woman dressed provocatively can be a sign that she is interested in meeting someone, but it is not always the case. First you must observe her body language and second you can watch how she is dressed. Anyway, it cannot be so easy at all, because they like putting you in a difficult situation and making you blush like a tomato if necessary.
If she is going sexy and coming with some friends, men mostly of them, this is the worst part of trying to approach her, especially because you will have many eyes appreciating her cleavage or legs going out of her mini-skirt.
On the other hand, it could be an advantage for you if knowing to approach delicately to her and to apart her from these blowflies, although the most probably thing would be to finish on a battle with the other men.
Everything necessary to become a seducer is being rejected so many times and to learn from the different situations. Doing mistakes and learning how to correct them would be the successful way for seducing a girl.