When chickens molt, you'll find what looks like an explosion of feathers somewhere around the roosting locations. It scares a lot of beginner chicken keepers into thinking there was an attack.
She is molting, which a natural thing that happens every year. Every bird species molts and they do it mostly when it starts to become cold, which can become a problem because they will actually be colder and weaker until they grow their feathers back. They molt so they can grow back in...