Thank you so much everyone for your prompt and kind reply. He did do a fecal float which was negative and suggested I still worm them, which I have not done yet (but will do tomorrow). I will get her some vitamins and keep watching her. We are in Brisbane Australia, so it is not cold at all - but I suppose if she is fluffing herself up, she must feel the cold? I will bring her in the house at night (bathtub). Again thank you everyone. I hope she gets better cause we have no idea what her problem is.
I'm sorry your hen is not feeling well. I am new to this chicken thing but have many books on poultry health and spend hours reading them.
A couple of questions...
What age was she when you got her?
How long has she been like this?
How old is she? How long has she been laying? Has she had any egg laying or "bad" egg problems?
What is her usual position in the flock? Pecking order?
Have you lost any other chickens lately?
Is or was a rooster paying to much attention to her?
Any big changes to the coop lately?
How does she look, fully feathered? Eyes and nasal passages clear? Any signs of wounds? (I did see that you had her to a vet and concerns about gleet and worms)
Is she eating and drinking regularly? Dehydrated?
Has she been "gapeing" opening and closing her beak, stretching her neck out?
Can you feel any lumps in her breast cavity?
Are any of your other hens showing signs?
What are the conditions of your coop? Size, is it crowded? Cleaniness, dust free, moisture levels, ammonia levels? Clean water? Good food, no mouldy feed? Could she have ingested anything? Poison, hardware?
If you find you have all the right answers to the previous questions, your looking at something else that needs to be treated with antibiotics or a natural homopathic treatment.
If she is a younger hen with no past problems in the flock health, and if she is parasite free, your still looking at numerous other things. All cause the stress you are seeing. I would be inclined to place her in a large dog crate away from the others is a quiet draft free place.
Step 1: I would treat with vitamins and electrolytes and a good dose of yogurt daily. No other food but chick starter, medicated or reg, mashed, warmed with a little water if you have to. See how she does for a few days. Improving? Great! Maintaining? Continue doing what your doing! Worse? Treatment?
Step 2: The problem now would be which antibiotic. What signs are you seeing health wise? Is it something an antibiotic could even help with? Personally if I were stumped, I would treat with nothing else to lose.
Keep in mind chickens get tumors and there is nothing to be done about it.
I would not treat her for worms until you have her health improved. Vet said he saw no signs right? If this is worms making her ill, he'd have seen them.
I hope this is helpful. Good luck
B.