If they've been seeing each other for about a week, you can open the door and let them mix, but it's probably best to make sure it's later in the day, before roosting, and provide irresistible treats spread out so there's something else to focus on and no need to fight over them. If there are any concerns about serious fighting it would be best to supervise so if blood is shed you can intervene and separate them in time. However some scuffles are to be expected.
It can help to provide an obstacle course of things to hide under and jump up onto so bullied birds can escape their attackers. Sometimes breaking the repetitive pattern of bullying is all that is necessary, and that's where obstacles can help.
Best wishes with the mixing.