the flock and the odd one

In the spring I hatched out four chicks (very bad hatch rate we had quite a few eggs) one chick died in the first week. The other three grew up to be two hens and a rooster. All are barred rocks. They are now four or five months old. Three weeks ago I aguried a hen who was living on her own In the wild. That's besides the fact because she is friendly. So without me knowing my mom took her out of quarrentine and put her in a cage in the chicken coup. Then three days later she felt bad for her and let her into the flock. Well the flock terrorised her (they didn't pull out feathets or draw blood. Just chased her relentlessly) so then She wouldn't leave the coup and one day she flew out and wouldnt come back. Felling bad from her my mom split the coup and run in two. I want her to be with the flock, but she needs to be okay with them. Today I put the lowest hen in with her and they were good. But then the hen (not the new one) became stressed out and I had to put her back with her friends. I was thinking if I got a low hen from another person and put her in with the new hen so that my new hen would be superior to that one then maybe I could introduce them together (once they became friends) thoughts? Ideas?
Thank you!