Was she separated for a time? Perhaps they're trying to settle the pecking order with her? Is there a possibility that she did something that upset the others? Is she sick or injured? You might have to separate her. Do they free-range?
With Sparkles (this happened to her), I let her free-range by herself all the time and had her sleep in my shed. She had been with her flock for almost a year and then she attacked some Black Australorp pullets. Nalla had decided to adopt those pullets when they moved into the flock and didn't approve of Sparkles being mean to them. So Nalla went to her friend Shiloh (Shiloh was second to top of the pecking order, second in command of the flock, had second to most say), and had Shiloh turn the whole flock against Sparkles. Next thing I knew, Sparkles' hackles was gone with horrible injuries all over and had the whole flock attacking her constantly. That's when I separated her. Sparkles was a RIR, and due to the injuries that the hens did to her, she had some hackles grow back white. I tried moving her into a different flock, but she wouldn't stay, so that's why I had her free-range all the time.
Perhaps your hen is dealing with something like what Sparkles went through?