If you are a good looking female you can wear trash bags held together with duct tape, guys at the gym are still going to look.
above the knee , below the knee, tank tops, shirts, men shorts, sweat shirts, sweat pants, capri pants, regular shirts, shirts that expose clevage to a degree, what ever
doesn't matter; if someone finds you attractive at the gym, you will get noticed.
plus think about this, some women work really hard to get to where they are at, so the gym is a place among many to show off, and why not, they earned it. if one can not show off at the gym, men or women, then everyone needs to cover up at the beach as well, men need to put on shirts and women wear one piece suits or the outfits before say 1955.
I go to the gym enough to spot the show boats, gym rats, juice heads, people that are there to really lose weight or are in some kind of athletic training and everything in between.
it boils down to insecurity if ones boyfriend is requesting his girlfriend to cover up or wear something that doesnt accent her assets.
now if one is dressing to get a reaction out of the boyfriend, because she knows it upsets him or she knows he has some insecurities then that is a different story i suppose.