It's not 100% attractive, they want attention, and all in all your pushing your luck for how much drama you get out of your life. But it's her life and I can only say live it the most miserably as you can cause girls will talk, guys will cheat or move on ( maybe) and people will use you for your body. I'm being real here no punches pulled.
It's their head, their body, they could do whatever they want with it. They are not hurting others, so who are we to judge? It shows confidence and the ability to not give a fuck what others think, and I think that's cool.