I had a silkie hen that was mineral deficient and her head was tilted so she couldn't keep it straight so I have her mineral supplement and she went back to normal. But it does sound more like an injury, I would keep an eye on it if I were you just to make sure she is not gettin worse.
There are a few things that it could be, either crook neck or a mineral deficiency. Crook neck will keep getting worse and there is really nothing you can do about it. A mineral deficiency can make the head turn and neck turn to where it can't keep it's head straight. Was there any injuries that...