OK; I finally got my password so I can give you an update.
I kept Nibblet off her feet for a week. She used her wee-wee pad, I carried her everywhere, I hand fed her (she's up to 4 pounds! She's usually 2.3/4). We went to the beach and she walked a little on flat sand, but I carried her most of the time because I didn't want her to strain her leg. No agility class this week. I walked her today, and I noticed when we got halfway through our walk that she was favoring her leg (even though she wanted to run- and did till I stopped her).
SO... We went to the vet and it looks like she has LP on the leg she was favoring. This is the first time she's ever had this problem, and she's 2 years old. She's been in agility/click a trick classes since she finished puppy class, and she loves it.

But for now we're going to have to stop. The vet said we could do surgery, or wait and see how she is with the Rimadyl. So she's on that (.25 pill twice a day for six days). No stairs or jumping or running (which means no chasing the cats and making them her chew toys).
So that's where we are. I'd rather not do the surgery, and if the Rimadyl works, that's the route I'm taking. She's not in pain, and it's probably just the inflamation. But if she's still favoring it, we'll have to have the surgery. I just get SO nervous about putting her under because she's so tiny.
So keep your fingers crossed for no surgery!!