Hi again
I'm sorry my comment came across as snarky and I will admit that I was a little frustrated when I typed it, because many of us have never had access to over the counter antibiotics and your comment about giving up your flock because you couldn't get them, was a bit insulting to those of us who have always had to manage our flocks without the use of such medicines. There is much joy but also some heart break in keeping chickens as with all things in life and sadly it is not always possible to cure sick chickens, as it is not possible to cure all people who are sick. The next best thing is to make them as comfortable as possible whilst they have some quality of life and my personal belief is to give them a quick end when there is no hope and that quality of life is no longer sustainable, but I appreciate that is not for everyone.
The only thing I would add to Wyorp Rock's excellent advice, is to make her a chicken sling or hammock, to support her in an upright position so that she can feed herself and be more comfortable. Empty yoghurt pots can be used for food and water and inserted into the hammock fabric (an old tshirt works well) or fastened to the hammock structure with cable ties (zip ties). Also put her outside near the other chickens in a protected (perhaps dog cage ) environment and give her the opportunity to spend some time on some grass out of the hammock each day, trying to move/support herself and even encouraging her to move towards a target like favourite treats etc. If it is Marek's, I have had some birds come back from some crippling paralysis by giving them exposure to sunshine and grass and the company of other chickens and allowing/encouraging them to move towards a target, be that, letting them out of the cage at night and trying to make their own way towards the coop or scattering a favourite treat just out of reach and gradually extending the distance each day. As long as they are still eating there is hope. Giving her healthy nutritional treats like meal worms, scrambled egg and a bit of cat food or meat or fish should help keep her interest in food and together with a vitamin supplement, boost her immune system.
Good luck with her. Hopefully Wyorp Rock will post some images of chicken slings/hammocks that can be made quite simply from everyday items as she kindly has before in such situations.
Best wishes
Barbara