I am so sorry for your loss. Most state vets will do a necropsy on chickens when you lose them to look for a cause of death, if you keep the body cold, but not frozen, and take it in or ship it overnight. Here is a list of state vet labs:
https://www.metzerfarms.com/poultry-labs.html
Is her left eye normal or also dilated. Usually one pupil being dilated means the eye is opening farther to get more light into the eye. The right eye is near sighted, while the left eye is far sighted. So she may not see things close up that well. Here is some info about vision in chickens...