My newbies I raised from chicks. When it was time (they were about 2 months young) to introduce them to my 2 established girls, Lucy and Nugget, we put a divider up in the pen so they could see each other and visit. Nugget was fine with the introduction. Lucy on the other hand, wanted to fight everyone. She was such a bully! We ended up leaving her in the divide and allowed the others to co-mingle. Being as we only have one hen house, we made a separate entrance and put a divide inside so everyone could be together safe and sound at night. I tell you, the lengths we've gone through for our girls! I'd say a good 2 months had gone by, I felt the youngsters were mature enough to take Lucy's attitude. They needed to establish their pecking order as they will do. Much to my shock, when they were finally allowed to be together it wasn't Lucy running the show! Whatever "discussions" they had through the fence turned it all around. Now they all reside together one happy family!
As for Grace.. She has a long story.. Lucy and her had a dispute long ago.. A few days later my husband found her face down in the pouring rain, unable to get up. He felt so bad he made her a corral in the mud room of our house. She was my BFF from day one, I had to do something to help her. As silly as it was to see, I soaked her legs in an epsom salt bath and massaged them. Every day. For a over a month. She was alert. Ate well. She didn't appear to be in any pain. And darned if she didn't lay an egg every day. So as it were, she became our house pet. And she started standing, if only briefly. Then she learned to walk again.. Awkwardly, she will rest every few steps or so, but she can still get around! But in spite of all her achievements, she was not safe with the rest of the girls. Last summer we made her a place in the utility room of our hen house. She loved the summer outside, maybe the company, not so much. She seems stressed out more than anything by the other girls; she'll stand tall and puff up and pick at them through the fence. But I'm afraid of someone were to stand up to her she'd get hurt all over again so she remains separate. Early last winter we almost lost her again, to an infection in her toes and toenails. So she is now back inside with us. I don't think she'll ever be able to join the others like she should. But she seems to be happy right here with us, which is nice. So she will always have a place within our home and our hearts.