It sounds like a respiratory disease such as mycoplasma (MG,) or possibly coryza. Make sure that you have overhead ventilation in the coop from one side to the other. Try to get her drinking fluids, and hou can make a runny mash of chicken feed and a little plain yogurt, plus some soft egg. But fluids are most important. You can use Tylan 50 injectable orally and give her about 1.5 ml 2-3 times a day for 5 days. Get it in the cattle medicines from most feed stores. The cedar is not good for chickens, but the symptoms sound more like MG. Here is a link with illnesses, and you can scroll down for mycoplasma gallisepticum:
http://edis.ifas.ufl.edu/ps044
http://edis.ifas.ufl.edu/ps044

