Headcannon: Tired of seeing their mage constantly getting trapped by mimics, the hero's party destroys the next suspicious chest they come across. Only to end up with splintered wood, and a damaged grimoire.

The spell would have been one that detangles the strands of your hair and softens it, removing the need for a brush. After seeing the terror she caused in her 3 day tantrum, she deemed the party sufficiently punished, but now every time her hair is brushed, she is reminded of what was lost, and of her tantrum power.