aaggjg - any discharge from nostrils? Do her eyes look normal? Is she eating and drinking? If I had to guess, assuming she has no discharge, I would say it is either Marek's or parasite overload. Check for external parasites (mites/lice) which most often are evident under wings, around vent, and on head.
If you decide you want to worm, there is lots of information here and elsewhere, but what I opted for was Safeguard liquid for goats, 0.5 cc per large fowl and 0.25 cc per bantam (Silkie), repeat in 7-10 days. I bought a box of 1 cc syringes without needles from Amazon when I ordered the Safeguard, but they also had the Safeguard at the local feed store.
If it is Marek's it is highly unlikely she will survive. If it is parasites she may, although once they are down it's tough. If it is something else (someone on another thread recently posted that his birds may have died from a leukosis (sp?), which I think he said was basically tumors that grow until organs don't work or until nerves or blood vessels are blocked) all you can do is support her and hope for the best. I'd say separate from the flock, but if she has something contagious it's probably too late for that anyway. I would still separate just in case.
I am very sorry, and am hoping she pulls through for you. I think you did the right thing giving her some polyvisol, and you can try giving her some scrambled or boiled egg, some scratch, anything she will eat. I will be thinking of you.
