I'm sorry that you lost her. If you want to find out if she had Mareks or if you want to find a cause of death, your state vet or local poultry lab may be able to do a necropsy. The body should be refrigerated and shipped or taken to the lab.
Wry neck or torticolis is a symptom of many different conditions. Head injury, Mareks disease, vitamin E deficiency, and other diseases that affect the brain are possible causes. Vitamin E and the mineral selenium are used to try it. Feeding can be a problem, if her neck does not relax enough to...