What is the best way to introduce new chickens?

[polloamante]

I've been taking my new chicks to see my older girls everyday and they seem to like each-other, very little dominance pecking. But when i introduced my new cochin bantam, she went after everyone else, shes so small though and my girls are huge! she is smaller than the silkie bantam, and she went after the silkie, the standard orpingtons, and ee, and she left the chicks alone, is this just too much stress for her maybe? or is she just more aggressive in nature?

 

[cubalaya]

slip them on the roost at night and keep an eye on them in the morning