When I was the head tutor of my college, I had a couple young girls who were barely 18. They were on my staff and dressed similar to your description (though no bikini's). Very attractive younger girls who wore very loose tops that... enabled things to be in view when they would bend over to help. Also wore fairly short shorts, and mini skirts that were slightly too mini. They also happened to like the see through silk tops. Though they never came in just a sports bra, they were still fairly distractive to my tutoring center and other students were definitely taking notice.

The situation is slightly different in that they were being employed by the school to be tutors but the distraction still applied. I took them off to the side one day and told them about how their clothing was not work place appropriate. This was their first job so I decided to help educate them on what would be work appropriate. In their case, they didn't realize that the clothing was an issue. Both of these girls liked to dress stylish and why they dressed the way they did. However, I had to inform them that this style of clothing was not okay for work.

They understood and changed to more professional looking clothing. Still wearing dresses or skirts but that were not super revealing and more modest. Totally okay by me. The damage was already done though because unlike your situation which does not seem to involve aggressive males, my school and in particular my frequent student visitors happen to have a decent amount of military men. Now don't get me wrong, I have the utmost respect for the military and I mean this in no disrespect to them, simply building the environment for everyone to imagine.

Unfortunately for one, he was a narcissist who also was more than likely dealing from issues with PTSD. He happened to take a liking to one of the girls and used his predatory nature to harass this girl (mind you this guy was also twice her age and married).

It started out with pet names like calling her beautiful or sweetheart and other things to lure them in with kindness like most predators do, and this made her feel very uncomfortable. He also was following her around acting like "a very friendly guy who wanted to be a part of her group". So She approached me about it and I made a mention to this gentlemen that his words to her are making her uncomfortable and that I understands he is "friends" with her but that she would like it if you didn't follow her around every where she goes. His excuse was "I am from the south this is the way we talk". I told him that this was understandable but his word choices and the way he interacts with her is making her uncomfortable and I would like for him to choose other words. He didn't like being told no and made a big stink about it as well as stating that... "if she didn't like it, she should tell him herself." Much easier said than done for anyone who is more passive/submissive walking up to someone who is highly aggressive and easily agitated.

It was also during this time, we started documenting incidents in Incident Reports so that if this became elevated, we had documented proof and witnesses because I had a feeling something was going to escalate more. A few days later, he came by again and went right to the girl who was sitting down at a desk and put his hands on her desk and leered over her demanding that she tells him what I told him to his face. Pretty much intimidating her when this girl is barely 80 lbs wet (she was actually 86 lbs for the record) and very tiny and he was well over 6 feet tall. I was not in the room at the time as I was TA'ing for another class but one of our fellow students stepped up to him in which the aggressor threatened to put that student on the ground. It was at this point, I received a text message about what was going on and excused myself from the class to come in to help settle the situation. I asked him to leave and when he refused, the librarian (who was a very strong woman and the person who oversaw the tutoring center as my boss) came in and told him he needed to leave.

He then used his narcissist mentality to turn from aggressor to victim and told us he was going to the dean because we are not allowed to kick anyone out or refuse students from entering the tutoring center and he was "just trying to get help for his class work". After the dean saw reports of the situation and talked to the witnesses, it was decided that this student was no longer allowed to be in the tutoring center while she was working. She was also escorted around the campus to her classes and TAing blocks by myself and other larger males to make sure he didn't interfere (which there was several times this gentleman tailed us or tried to walk right into me while escorting the girl). She was also provided security guard escorts as well when ever we needed it.

TL;DR: Moral of my story, a girl may not realize her dress is not appropriate. her wearing of yoga pants could be because she intended to go to the gym after class and didn't want to change this particular day. The see through blouses might be because bras, especially in the summer time, can make the girls get a little hot and uncomfortable and she might have been feeling warmer that day. You can't assume that she is intending it for attention though it does appear to be this way. However attention seeking would be done a little more frequent than once or so a month in my experience. It would be best though to approach her so that she doesn't end up having any aggressive, possessive males try to corner her like I explained in my story. Unfortunately other people shouldn't dictate how you dress, but some times a level of professionalism, and personal safety need to be considered too.