Why is the cat doing this?

Hello!

We started feeding this stray and we believe she belongs to someone because she very clean and well behaved, but she hasn’t left at all. So we’re just taking care of her until someone claims her. She’s been with us for about 5-6 days now, and recently started shuffling on her two hind legs in a low position. Not really wiggling. More like waddling. She also started walking really low to the floor and started being very vocal meowing and mewling everywhere she walks.

Does anyone have an idea what it could be? She doesn’t seem like she’s in pain.

Any insight is appreciated! Thanks!