I ordered mine online, maybe check Pinterest if you’d prefer the homemade route. But I got mine for $10 on amazon to try and help my current cockerel suffering.
The full paralysis doesn’t come until later. It starts with walking strange and using wings for balance. Eventually they become completely paralyzed and can’t eat or drink resulting in their death. It’s possible she could just have been pecked in her head causing the issue ( I was hoping that...
Sounds like mareks disease. I have lost one pullet to it and now a cockerel has it. I would give her some extra vitamins and electrolytes in the water if you aren’t already.