You might consider separating her from the others along with another that won't pick her. I had a sweet Polish pullet that got pecked on the head until it killed her. I had no idea it was that bad. I had been putting no-pick on her and she was not even pecked bloody, so I didn't realize she was in mortal danger.
Now, I'm assuming that's what killed her. She had not been acting ill, and the rest of my flock were healthy, too. No other injuries that I could find. So it's possible that something else was the cause of her death, but I can't imagine what it would be.
Good luck to you!