You might also put out an extra feeder or two so the red skinny hen gets a chance to eat or separate her at chow time - so she can eat without being bullied
Welcome to BYC. It would be great if you could observe the birds without being seen, to discover just what is happening . If you discover another bird causing this damage to her, I would put "pinless peepers," on the culprit. That should stop the damage/attacks.