First off get that chicken QTed FAR away from your flock ASAP do not wait till the am...DO NOT HANDLE HER or let her touch you or your clothes/gloves and then handle your other chickens without a complete clothing change and hand washing, she shakes her head and your getting germy chicken snot on you even if you cant see it...be aware of your shoes also. Once segragated give her Sulmet in the water and/or auremycin in the feed and see what happens. I would also give my others some just in case Sulmet in the water and bleach your coop. Could be CRD or a number of other things....er on the side of caution....the head shake and the noise is indicative of a VERY sick chicken, walking admist your very healthy looking birds! EEEEEK!
With chickens, if they even LOOK cross eyed at you, get a runny nose, a crusty eye or do a head shake and gasp....and you dont have the heart to cull....then you get them FAR FAR away from the rest of the flock as fast as you can and medicate and disinfect EVERYTHING and follow STRICT bio security measures. 1 sick chicken can mean 100 DEAD chickens...take it very seriously.
PS DONT EAT ANY EGGS for about 3 weeks after dosing with Sulmet or any other antibiotic. You can hatch them, but dont eat them!