She’s gorgeous!! Luxating patella (floating knees) is common in chihuahuas. There’s different grades, grades 1-4, depending on how loose the tendons are in the knee. Just keep an eye on it, if it looks like it’s bothering her, talk to her vet. It may never bother her, or it can get worse and may need surgery. It’s hard to say. I have a French bullhuahua that has it, but other than walking with a little skip every once and a while, it doesn’t bother him much.