Ok, shouldn't be mareks then.
If you have an old crate, box or anything you could put her in and keep her warm that would help.
Make sure she can reach food from everywhere.
If its contagious, it could spread to other hens. If thats the case and it does spread, Its worth taking ONE of them...
Whats her approx age?
Try to feed her yogurt, and make sure she is seperated from the others. (I'm presuming you have a flock)
Info on mereks:
http://www.shagbarkbantams.com/page9.htm