Ouroboros Spine The trouble was...

As a very little kid Kau did not know yet the boundaries (or limits to her parent figure's patience), therefore, when playing she easily got carried away. Not only in terms of time, but also intensity. If not stopped at the right moment, she could easily become violent (as a puppy - v-e-e-e-e-ry annoying). 

So, when the Aiolos had had enough with her trying to eat his paws, he took her by surprise, pinning her to the ground. At first she tried to squirm out of the hold, growling and yelping simultaneously, but eventually she calmed down and ceased to resist. Consider lesson learned. For now.