At least with employee one going out for surgery, you and your staff will be able to see just how much the stress level goes down while she's out.
Employee one may have a personality disorder, but it could also be that she is resentful of others and feels that she's not being recognized for her work. I've seen a lot of this nonsense of thinking that they can be supervisors or as we say "lord over" other employees just because it makes them feel better. Upon employee one's return, someone will need to document her behavior and the first time she acts up, call her in and advise her that it is the only warning she's getting because the next time will be the walk to the door.
She sounds like a bully who needs to express her self at others. I'm sorry you are having to deal w/this. Let's home she opts to leave and not return.
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.
