I wish I knew what advice to give you but without being there to see for myself it's hard to tell, but you know Katie best and if she's not acting right I'd push to have her taken in so the vet could give her a look. I always get very paranoid the moment one of mine seems to be not quite acting right.

You just noticed this change for the first time today? If she just walks a bit funny but otherwise her appetite is fine and she's acting mostly herself it sounds like she could have strained a muscle or something.

Keep us updated and I will keep Katie in my thoughts and prayers!