Isolate her from the rest of your flock. Feed the rest of your flock first and then feed her. Alwayse touch her last and then put your clothes in the wash, wash your hands and lysol your shoes. It sounds like she has a virus and you need to maintain biosecurity. DO NOT put oil down her throat, if you don't know what you are doing and you get oil in her lungs, she WILL suffocate.
I would deworm her with fenbendazole after isolating her. Get the paste fenbendazole for horses (don't listen to what your feed store person tells you) and give her a pea-sized portion once a day for three days. Just put it in her beak and she'll swallow it like peanut butter.
After doing all of that, just keep her in a clean, warm environment and support her. If she develops a secondary infection, switch antibiotics, try a terramycin or enrofloxacin.