Vitamin therapy won't hurt her. But I suggest you get the bottle of B-100 complex. It has the highest amount of B-6 in it, a B vitamin that mends nerve connections. I'm treating a pullet right now with it and she's shown improvement that's been surprisingly encouraging.
It could be Marek's. But it's easy enough to buy a bottle of B-100 complex from Walmart and vitamin E 400iu and a bottle of selenium and give her one E and a quarter tab of selenium each day, and half a B -100 complex twice a day, and see what happens.