Sounds like silkie syndrome. It can be caused by a bump to the soft spot on their head or nutritional deficiency. Get some Polyvisol(NO IRON) infant drops drug stores have it like
Walmart etc. Give her 2 drops 3 times a day. If she won't take it off food put, the dropper just inside her beak so she can push it out if she won't swallow it.
Get some vit.E capsules, pierce one and squeeze a couple drops out of that once a day - sometimes you can get them to take it off food which is the easiest way.
Now to her, otherwise is she acting normal, eating, drinking pooping? Can she raise her head at all? Make sure to give her a shallow water dish,with some clean pebbles or marbles in it so she won't drown- if she can't lift her head out. You can massage her neck very gently a few times a day in a more upright fashion. Make sure she is warm enough (I assume she is in a brooder). If other chicks are in with her = you may want to make a partition so they don't climb all over her and tire her out.
This is NOT CONTAGIOUS. If a vet thinks there is swelling around the brain he may treat with prednisone. This is something you would use ONLY by vet's order and exactly as he says it should be used. Sometimes the chick(or bird) seems to improve and then relapses - don't let that upset you. I tis fairly common. Otherwise, recovery itself can be a slow, gradual thing. I have never heard of a chick dying from this but, some owners are so distressed by the sight of them - they cull them to make themselves feel better.
My friend had a silkie mix cockerel with it but, he had complications, seizures etc. Everyday she thought would be his last but, he is several years old now, and you would never know all the troubles he had. He is the protector of her house chicken flock -silkies and serama hens.
You may also want to post on the "Silkie thread." where the folks may know if anything else has been added to the treatment.