The "lets get this FA off the aircraft because she is severely p%ssing me off and I don't want to be distracted in a while when we are in a crucial phase of flight" theory, seems almost ridiculous,
Don't underestimate the dangers of distraction in a flying environment. You
have to stay ahead and be on top of the aeroplane with your attention on what is happening, not other problems. I remember long ago, the US Navy discovered that pilots with problems playing on their mind (from home usually) or in marital breakups had a significantly higher accident rate. Quite simply if you try and fly in that frame of mind, you become a significant danger. That is why I have been saying all along that such a decision can be shown sometimes to be a justifiable course of action if it removes the problem. There's too much here to produce instant guilty verdicts I'm afraid. Something ugly going on. The company needs to sort it. It sounds to me like the company has allowed these people to carry a very unpleasant burden for 24 years.