Kitty limping

It's not bad - and it's not stopping her from doing anything.

She goes to the vet on Thursday anyway for shots - should I call or should I wait?

All I can think is that she plays rough with her sister. Maybe she fell off the couch or somehting. She doesn't cry or mope or anything?!

If she got hurt while playing it's possible that it's a sprain or other minor injury. I am not an expert so I could be wrong. You could call the veterinary clinic and ask if they think a vet should look at the leg sooner than Thursday.