Oh sorry that's concerning. What is she eating? What are your temps like? If you are not seeing results with the Corid then toltrazuril or a sulfa antibiotic are the next medications recommended, Corid is effective most of the time.
Give her a Corid drench. It will really help. And make sure that you're not giving anything extra like vitamins. Just water and feed.
https://www.backyardchickens.com/threads/corid-oral-drench-instructions.1211991/