If she passes (hopefully not) you could get an autopsy done by your local State Extension service to determine cause of death....I found her with stretched out wings eyes closed still breathing this morning and gave her some water drops with my finger. I rested her head so it is not laying in the wood shavings... she is still breathing and swallowing...Oh I wish I could do more. :/
When you clean out the coop make sure it is well aired out before you put her back in, sometimes the fumes can be irritating to the breathing system,