To a certain degree, this will have to be tolerated as it is typical pecking order behavior. Put several extra food and water containers in widely separated areas so there is always a place the reintroduced girl can go for nourishment. If all girls are back in the same coop at night, make it a habit to get up extra early & let them out so your girl isn't shut up inside with the others for long periods with no escape. As long as the reintroduced girl isn't being injured -- she should be fine. If viciousness is such that she is being injured or if she stops eating/drinking and mopes by herself- probably time to take action. What has worked for me is to put the worst perpetrator into a pen embedded inside the larger pen area. Perp gets to see the others getting along well & enjoying their time. After a couple days, let perp out with supervision. If she behaves, may work. Maybe during her separation, she fell a notch on the pecking order & is ready to be moe humble. If not, back she goes for another 24 hours, etc. Alternatively, you can put the hen lowest on the pecking order into the embedded pen & try the same tactic... but if she's doing fine with the other hens, I'd be inclined to send the perp to embedded lock-up. For what it's worth, this has worked for me in the past...
