My sister has a toy poodle named troubles who is getting on in age and she has aurthoritis (i know I spelled that wrong) and even though she has all four legs, she only uses the front TWO! She walks on the front two legs and her hips and back legs are up in the air cause she can't use them. She is still fiesty and spunky and gets along great! She even tries to run away all the time because my sister also has a scottish terrier and troubles hates him
I'm really sorry you have to go through that but I think she will be just fine. It will be sad for you to see but after you both adjust it will just seem normal for both of you. Best wishes