A chicken is never too old for Coccidiosis. All they have to experience is a strain that they haven't encountered before. They will have no resistance against it.
I am guessing that you are dealing with a respiratory infection. The best thing to do is to get Tylan 50 and start her on it immediately. You can give it by injection or by mouth. You can put it on bread or some other goody and feed it to her or, just dose her with it. She sounds very ill...with that pale of comb. You need to get some protein into her...mealworms, scrambled egg, chicken livers, cat food...you can try a mash with crumbles, yogurt and water.
Poly vi sol, without iron, .5mls per day, would be a good thing to do for her also. Good luck with your pullet!
If she has been sick for a week, what have you been doing to treat her so far?