Try taking the attacker away when you reintroduce the RIR. Put the attacker in the box for a couple of days. Now if all of them challenge the bird when she's reintroduced, you have to let it go a bit. But don't let them get too carried away. I have a EE that got attacked by a dog a couple of years ago. She was in rough shape so I had to take her up to the house for almost a full week. She was no where near 100% when i took her back out there. I put her on the ground, and all the chickens came over to check her out, acted like she was a total stranger. As they crowded around her, she straighten her self up and stood as tall as she could. Couple of birds pecked at her, she pecked back, grabbing a hold of some of them. This battle of chicken wills went on for 15-20mins. Then the queen hen came over and grabbed her and forced her down. The EE didn't put up no resistance to her, and after a couple more pecks, everything just kinda mellowed out.
If it's just one attacker, take her away and give her a time out. If it's the whole flock, just let it go, and stand by in case it gets out of hand (Blood being drawn). A lot of what they do is not as bad as it looks. GoodLuck with them