When many people post, they are not really sure how serious an ailment is. Sometimes when advised that it is indeed serious as well as time sensitive, and a vet visit is recommended, they then proceed to take that action. If somebody can't take that action, they can't.
Hence why I try to always say "if you are able......". A vet will be recommended when believed to be the bird's best chance of survival.
OP, if you are able, another alternative would be to call Peter Brown at First State Vet Supply (
http://www.firststatevetsupply.com/). Peter is extremely knowledgable and can direct you to meds if he thinks they would be helpful, or can send them directly from First State Vet Supply. Hopefully he is available today if you call. He has been an incredibly kind and helpful person time and again to many.
I hope your hen will get better. Any which way sliced, this is time sensitive, so I hope you can find out how to help her. Continue to keep her warm and comfortable and hydrated, as you have been. Administer 3 drops Polyvisol childrens liquid vitamins daily - use dropper and dribble gently along her beak line so she swallows on her own and doesn't choke. The stuff tastes like crud so try to follow with something tasty like cut up blueberries, if you can coax her to take them (I know this may be very difficult right now - that she is not eating means she feels dreadful). If she has a bacterial ailment she likely needs the right antibiotic stat in order to survive. A few years ago I had a hen get terribly lethargic suddenly - rushed her to the vet (which was a challenge on Labor Day as all offices were closed but I left emergency messages all over creation). Antibiotic turned her right around - blood work that came back later did show results consistent with infection and/or inflammation of unknown origin. She likely would have died without it. It's 3 years later now and she's the picture of health. Never found out what got ahold of her but it was wicked fierce because it took her down fast - she was fine in the morning and unable to lift her head by afternoon.
JJ