I know how hard it is to have your special dog hurting. I'm so sorry. Please give her some lovin' from me, ok? I hope she has many happy years ahead. I'm glad you didn't know about byb because then, she might not have had a life with you. And don't forget that they make the harnesses for dogs. That way she could run all she wanted once she got used to it without damaging herself further. I hope there's better days ahead for you all.
Here's an example:
http://www.dogkarts.com/