I really think you need to identify the top three bullies and keep them away for about a week. As IheatNH said, try to separate them too. If you have any dog crates that will work fine for keeping them in. Maybe some friends have some pet carriers you can borrow? Then introduce them one at a time, but not before at least a week so the abused hen will have time to adjust to the new pecking order. It appears everyone is pecking on her, because, the instigater is starting it. Try removing those birds, who ever is the first few birds to start it. Remove them. Let a new pecking order establish. When the old birds come back, they will have to deal with the new pecking order by themselves, and they will be more worried about the top of the order than the bottom. The bottom will get some attention, but not excessively so, I would think. Wait a few days inbetween to introduce each bird back. That's the only thing I can suggest except putting peepers on all the meanies.