Oh, and you should expect each of the chicks to feel a little stress when you start moving them to the empty brooder. Don't be too quick to move them back or to move them in larger groups because you are worried about them. It's that stress and desire to flock with others that you're hoping to capitalize on in order to get them to accept the little one. You want those first couple chicks to go through the process of thinking "OMG! Where did all my friends go? Oh, who are you? I don't know you, but being with you is better than being alone. Now you are my friend, too!" Then you add more chicks and they go through the same thing.
The stress/fear makes the instinct to flock override the instinct to establish a pecking order. Some pecking order stuff will still happen, but will hopefully be lessened because they will be more apt to see her as having been part of the flock all along rather than as the new girl.