Doesn't botulism also have loose feathers?Does she free range in any areas where she may have gotten hold of a rotten animal or fish carcass, or vegetation? Botulism is caused by a toxin found in those things. When you describe her neck turning to the side, does it seem like a spasm that could be wry neck or torticollis? Keep using the vitamins, especially B1 (thiamine) and E. Is she able to stand or walk? Is there any chance of lead poisoning? Here is some info about botulism and wry neck: http://www.thepoultrysite.com/diseaseinfo/19/botulism
http://oureggbasket.blogspot.com/2013/04/wry-neck-or-crook-neck-understanding-it.html
http://www.browneggblueegg.com/Article/Crookneck/Crookneck.html
What does her poo look like?