This does not really sound like Marek's to me. Marek's disease (from what I've read) doesn't usually cause curled toes. It usually paralyzes the legs and (sometimes) the wings.
Your description sounds more like Botulism, or poisoning. Botulism first paralyzes the legs and the wings, and then spreads throughout the body. By the time it reaches the head/neck, treatment is rarely successful. The organism that causes Botulism is found in rotting vegatation, fruits, or food, as well as in wet litter, etc. Treatment consists of a molasses or epsom salts flush. I'd give a molasses flush, as epsom salts will dehydrate a bird even more than a molasses flush. Make a solution of four tablespoons molasses and one quart of water. Give this mixture as the sole source of water for no more than 24 hours. Give her some from an eyedropper if she can't drink on her own.
Vitamin B deficiency is a possiblity, but the onset of it would not occur so suddenly. Still, you could try giving her some polyvisol infant vitamins (without iron).
I hope your bird gets better soon!