She was very good at her job and valuable to the company, so he didn't have a lot to complain about, but that didn't stop him from undermining her every chance he got. However, one day she came into my office and announced that she had finally addressed the problem and asserted herself. In other words, she decided that she'd had enough and wasn't prepared to put up with this behaviour any longer. It was risky, but she was prepared to take a chance. Things improved after that.
Abusive behaviour is a strategy that some people use to control situations or other people.
In a sense, it's a weapon being used in a power struggle. When I encourage patients to stop putting up with this abuse, some think I'm suggesting that they become dominant and take control. This would be a role reversal which most people would be afraid to try. It's not what I'm advocating. I merely suggest that they stop participating in the perpetrator-victim struggle that's going on.