Oh dear. It sounds like your chicken may have developed wry neck. In chickens it is a vitamin deficiency. Vitamin E and selenium. I am treating a chicken right now for the same thing. Mine has had it 4days and is not showing much improvement. So, I will tell you what I am doing, and hopefully so one with more experience will pipe in. I swaddle my chicken in a towel & gently straighten her neck back to where she can eat. I have to hold/pull the feathers on the back of her neck to assist her in eating so her neck doesn't twist back around.
I am feeding her a mixture of scrambled eggs, a teaspoon of yogurt, and a bit of chick starter. For drinking I have electrolytes in water, vitamin E capsules squeezed in and selenium tablet cut into 4ths & crushed up. The big thing is to make sure she stays hydrated. Working full time, I'm pretty sure this has been my downfall.
You may also have to bathe her daily. Good luck with yours. Let me know how she is doing.
