Where do you live? It is hot and do you have mosquitoes out? I cannot tell from pictures, but knowing the climate would help. Mosquitoes are one of the common ways that fowl pox virus is spread. Could she have been pecked?
Sorry that she is still ill. Can you describe the symptoms you have been seeing? Does she have sneeze/cough, gunk in eyes, nasal drainage, as well as gasping or noisy breathing. Tylan 50 found in cattle medicines at feed stores can be given to help MG or coryza. Canker is treated by metronidazole (FishZole,) available online. Swelling inside the beak can be from canker or trichmoniasis, but some respiratory diseases may also cause yellow caseous plaques inside the thoat. Is she drinking plenty of water, and eating? Try some wet chicken feed, chopped egg, yogurt, and vitamins such as Poultry NutriDrench are good to use.