I am really sorry that she died. I would refrigerate her body in a plastic garbage bag, and call your state poultry vet for a possible necropsy and testing for Mareks. I would be concerned about her having Mareks disease. It may not be that, but would be good to know if the disease might affect your flock in the future. Here is a good link with a list of state vets:
http://www.metzerfarms.com/PoultryLabs.cfm
http://www.metzerfarms.com/PoultryLabs.cfm
