The vet said she has very weak back legs and you can see her really struggle to walk properly. Are there any ways to help her get stronger? I'm scared if I take her back to the vet they'll tell me something else is wrong and I'll lose her.
You can always try and massage them some, perhaps three times a day. Do it as a sort of play if you can. Make also sure she gets good nourishing.
Soon it is time to deworm. Do so.
The first time you wrote this, I though for myself; what, three weeks AND sick in pneumonia, of course she does wobble and have weak back legs. What a problem where there is none...
But you tell now, she is much better now, a week older, and still weak and wobbling?