Help! Chicken stopped using one leg

I have a 6 month old Belgian Bearded d'Uccle. About 4 weeks ago, she stopped using her right leg. I found her with her 2 sisters sitting in the pen with one leg forward, like she was doing the splits. I took her to my veterinarian who said she may need an ex-ray and she was that she was slim. Over the next few weeks, I isolated her in a box full of wood chips and grass in the house. Last week she began to stand up on her own however she still cant put pressure onto the right leg- it trembles when she tries to move on it She cannot move forward, but is more comfortable stumbling backward. I dont know what else I can do to help her. Please Help!