How old is she? Dehydration can certainly cause those symptoms. I would make sure that she is drinking some electrolytes in her water for a couple of days, and eating. Feed a little water in her chicken feed, offer a little cooked chopped egg, or some tuna or liver if the egg doesn’t appeal.
When a young chicken under a year old suddenly loses balance, we get a little scared about something like Mareks disease. Mareks make show up to cause loss of balance, weakness or paralysis of one leg, or drooping wings.
Many things can be the cause so it is good to rule out being egg bound, or having a leg or foot injury. Mold in feed can cause similar symptoms.
I have an older hen who lost the ability to balance back in the winter for about 5 weeks. She could move her legs, but just fell backwards or to the side. I wasn’t convinced that it was Mareks, so I diligently fed her 3 times a day putting water into her food, since she would not drink. She regained her ability to get up and walk outside, and several months later, although she wobbles a little, she roams around our backyard all day long. She is not able to jump up on a roost, though.
The main thing is to help her get food and water, and prrotect her from bullying or harm. She may need to be separate in a pen or a dog crate with food and water while you observe her.