Weapons can be hidden under a head covering of any kind .. long/short hairpins, razors, small blades. That is a simple fact, all of your ridicule notwithstanding. That would be ANY head covering, be it golf/ball cap, sports hat, fedora, the hats the Hasidim wear, yarmulkes, birettas, kamilavkas, berets, hijabs, mantillas, Amish bonnets and men's hats, etc. etc. none should be exempt ... yes, not even Muslims.
Can't imagine what you would say if you were to be informed that she could have required a body cavity search as well. SCOTUS 2012.