It's quite possible for her to be lacking in certain ways. Perhaps she went without oxygen a bit too long during the birth. And/or did not get enough to eat in those first crucial days, because of her disabilities.
She will need a very special human, is all. The rescue should make sure that any potential adopters understand that this little girl has special needs. It would be awful for her to be adopted by the wrong person and pitched out on the street because she sometimes forgets to use the litter box.
If your husband wants to adopt her.........maybe she's already found her forever home? You wouldn't be the first with a 'failed foster'