I hope that didn't sound harsh to just tell you to cull. I doctored my hen for 4 weeks as she looked like this and it became very time consuming. I realized that she was in pain and had planned to cull her the day she died. I felt bad that she suffered for so long with it. Sometimes they just get too far gone with the disease or have overlapping diseases that make them so weak.
If you want to treat, you can try antibiotics. I only had Duramycin-10 available at the time and mixed 5 tsp per gallon of water. Can your hen see to eat and drink? You may have to water her with a dropper and if you can't get her to eat you can dissolve layer, grower or even dog food in water and dropper that into her. There are some really good posts on tube feeding here also. Hope this helps.
