I would think when she is eating and drinking it probably is not an injury... I would start her on the B complex immediately - the sooner the better if that is what is wrong, and it won't harm her at all if it turns out to be something else. I believe you should see some improvement pretty quickly if it is working, a few days would show you. Either way, if she is still not walking in the next few days I would make her a chicken sling/chair as it will keep her up out of her poop and prevent her from hurting herself whilst stumbling around. If it is Mareks, time will tell you that also. I believe the only sure way to text for Mareks is once they have passed via necropsy. I hadn't thought of a bone deformity which @Eggcessive posted about, and I am unaware of how you would test her for that so again, I hope others will help you out there. When you start her on the B complex keep us posted here if you can to let us know how it is going?