User blog comment:Miskos3/Fairy Tail Episode 259: Tartaros arc: 00:00, Review/@comment-24784846-20151114170157/@comment-7418318-20151114171023

There is another good explanation.

Kyouka only deactivated the "normal" five senses, but we've had mages in Fairy Tail feel magic time and again. This magical sense might well be seperate from touch, hearing, smelling, seeing and taste.

But then we've also seen Demons sense magic power, so why would Kyouka overlook this sixth sense? Maybe she couldn't deactivate it due to this sense working different when it's based off of curse power. If she can't fully understand a sense, she might be unable to deactivate it in others.