Here are some resources for necropsies, by state. You can call your nearest and get particulars on delivery and cost, if you are close enough you can often drop them off rather than ship. You can also call your state agriculture dept to ask for info. I've also attached a link that shows how...
I'm very sorry for your loss. :hugs
It's always a good idea to consider a necropsy, that's the best way to know what happened, and often the only way. Different illnesses can present with very similar symptoms. I'm so sorry you lost her.
She's probably having too much difficulty to get up on a roost, so she's staying on the ground. If the vitamins help then when she's moving better and more balanced she may start going to roost, or you can start putting her up there until she goes on her own. For now, make sure she's safe from...
She just started this? First I'd get her on a super B complex tablet or capsule daily, human ones. See if she improves with that, riboflavin deficiency can cause hock sitting and some of the other B's can cause weird neurological symptoms. The B's are very safe. It's best to use the complex...