Just add some information about her: All my chickens are carriers of Marek's Disease, so they do not have great capability to fight diseases. The Corid I gave her was 2 teaspoon per gallon water. I just found out it should be 0.1ml per pound weight if feed directly. I will give her 0.4ml when I get home.
I always do 2 tsp/gallon of corid and it always seems to work well. Just remember not to give any vitamins at all when giving corid and to mix fresh daily.
ETA, I just use an eye dropper or make sure to dip the break often to make sure she's getting enough.