yes. You need to get her eating and drinking first of all. If she won't drink, you could try moistening her feed and adding a little applesauce or yogurt to tempt her. Or oatmeal. Grapes...chop them up, they're juicy. hens with Marek's or neuro diseases can live. But first evaluate her for a day or so and see what other symptoms she has. There are pages of information on BYC about Hypericum and how it can cure Marek's. It worked for one of our hens, it was a miracle. Lots of people say that. If she quits eating and drinking altogether, you will need to tube feed her..it's not difficult, but I don't like to do it, I think it's hard on the hen as far as stress. But they gotta eat and drink to live. A lot.
Search Hypericum on here and you can decide if you should try it. But the unsteadiness could be from a lot of things, so that's why I say evaluate her.