Wry neck comes in all kinds of different forms. It isn't just a neck thing. If you would try the vitamin E, it might help us get to what's actually wrong by process of elimination. There is no other way to do it because we are out here in internet land, not physically there with you and your hen.
I hate to blurt out the worst case scenario, but it sure looks like chickens I've had in my flock that made it to a few years old and then became symptomatic with lymphoid leucosis, an avian virus similar to Marek's. My flock carries the leucosis virus. I'm very familiar with it in its many forms.
However, we should try other things first before we talk about this being one of those deadly viruses. What I recommend trying, besides vitamin E 400iu once a day with egg, is vitamin B-complex, one table a day for the next two or three weeks. Pop these pills right into her beak. These vitamins can repair damaged nerve connections. Get them were you buy people vitamins.
You said it hasn't been hot there. But has there been anything that might have caused this hen a lot of stress? Predator attack? A vicious toddler attack? Attack by another hen? Rooster aggression? Stress and subsequent shock can produce symptoms just like your hen has. The treatment for that, even if you don't necessarily suspect it, is give her sugar water, one teaspoon sugar in one cup water.
Starvation also produces these same symptoms, so the sugar water can raise glucose and provide enough energy to get the hen standing and eating again.
Our goal is to help you get this hen well and back to normal, not come up with a diagnosis. By trying each of these suggestions, you are doing things that can return a weak hen back to normal as long as there are no other underlying medical issues.
And, if you do all these things that have been suggested, and none of them work, then you are closer to finding out what's making her sick.
