I didn't witness it myself, but apparently Kelly took a spill at swim class. She was in line to take the ladder into the pool, and instead she hit a slippery patch (not running or misbehaving) and landed quite hard on her butt.
When I got home, she was taking a nap. She was trying to flee the trauma, I guess. She got up once kinda dazed and still asleep, and wandered about until we directed her to the bathroom. After a bit more rest, she got up and seemed quite chipper. After I put her to bed tonight, she seemed totally normal.