Welcome to the forum.
If the Amberlink wasn't really harming the Black Star, but just trying to 'show her who's boss', then maybe it is best to let the chickens sort it out. It sounds like you have provided all the chickens need. Maybe one other thing is some obstacles so that the less dominant chicken can get away, or hide from one that is aggressive.
Chickens live within a pecking order, and sometimes they don't establish it diplomatically. We humans interfere because we don't understand. Once the pecking order IS established they will calm down. When you take your Amberlink out, when you reintroduce her the pecking order will need to be re-sorted. I think a short removal, a place for the Black Star to shelter or run away from the Amberlink, and diversions in their life, like places to scratch, dustbathe etc. will be helpful.
I had one hen that I thought was too aggressive, but once she was firmly established she settled down nicely. Now I am going to combine two sets of chichens, and will have to see how they reestablish their pecking order, but I am going to leave it up to them as much as possible, unless one is REALLY in danger. Chickens (and other herd/flock animals) sometimes push each other around, much to our dismay. Eventually they get their hierarchy established, and peace will return.
