OK, honestly. She CAN wear a bikini, but because of shit like this it's really not a good idea. I CAN wear anything I want. I don't because of this little notion called self-preservation.
This, a thousand times this. I COULD wear whatever I want, but I know what kind of attention it brings because I'm er... top heavy... so I don't put myself in that position because it's uncomfortable at best, and can be really scary at worst.
You can make a choice to mitigate unwanted attention. Not to say that if I wore some boobs-out top that I would then DESERVE any unwanted attention (like the rape comparison made earlier), but I certainly should expect the possibility, based on past experience.