I've introduced a few times, and I always have better luck when I have several to introduce at the same time. Just one, they always get picked on worse. So like the others have said, I would get a her a few friends and introduce all at the same time. With my last introductions, I had 16 pullets to introduce to 10 older hens. I kept them seperate at night and would let them free range together during the day for a few weeks and now they are all together and they seem happy and fine. There will be a pecking order, no matter what you do. So she will probably always be at the bottom, but if she had a few friends it would help. Good luck.