the sheer audacity of being struck was enough, not to injure the woman, but send her into an ego-driven fit of disbelief. having led a cozy life, she was not used to being struck - in even the slightest way. so when her head was tapped... she just lost it.
I'm pretty sure it is, but damned if I can find it.
Also, I'm 99% certain that if that woman in the headdress was the one that got tapped with the folder then this would've been a much different scenario.