I wouldn't contribute it entirely on the TS for the insults. A lot of the nasty behaviors is deep roots for many yrs. It will not change overnight. This is the 1st fact TS should realize. Its does not mean she is a mean DIL or anything. Her MIL is nasty period.
But, what can be done to improve it? There are lots. But it comes with effort. So, the question, whether she wants in or out. If she wants in, then she needs to do things that would facilitate that long term goal. Not work against it and feel absolutely miserable about it.
Sheena, I wasn't a patient chap to begin with. I'm aggressive and quick minded in nature. But after all these yrs of fighting, reacting, it gets me no where. I used to screamed and curse my mum in anger, threw things, slammed doors, smashed and banged my head on the wall. Reacting in anger does nothing. There was once, my mum called my mobile and scolded me in office. I responded angrily right away and stormed out of the office.
When I came back and apologized to my colleague saying I couldn't take it at the moment over what she told me. He just simply told me one thing. You can choose to let it pass. No need to react to it. That got me thinking.
"you already said its your mum, your biological mum. After all, blood is thicker than water, and there is no overnight animosity between you and your own mum. But my MIL is not my biological mother, I am not insinuating that I dun regards her as my mother, just that its different."
I disagree. The blood isn't the importance. I love my MIL very much too. Rather, I cherish and appreciate the folks for who they are. I don't have a expectation on how they should and should not be like. I completely understand how important they are to my partner and that makes it important for me too. As explained, my MIL is a very negative person herself and my wife is often getting upset over that. I'm blessed in that sense my background prepared me well. I really respect my MIL and know how important she is to my wife. That's why I constantly reminded and rationalize things for her.
Just yesterday, I was listening to MIL telling me all the stories about my BIL ex-gfs. And how each of them tried to make her and her precious son fight.
I listened with empathy. No need to react at all.