Anyone else’s grown ass partner afraid of standing up to their mother?

To keep an extremely long story short; my MIL is ridiculous. There are components of maternal narcissism where she feels her son is an extension of her alongside cultural clashes as she’s from India and I am an American white woman. I’m not typical traditional Indian wife material that she is familiar with nor will I ever be. My partner and I have lived together before marrying, I refuse to have us all live together once we marry (he refuses this too), and I don’t call frequently because she makes me uncomfortable.

All of this has caused her to lash out at me several times. She has called me stand offish because I didn’t help her cook a whole meal once, she has called me passive aggressive because I didn’t put food on her plate once when we all went to a buffet. She has called me audacious because I don’t call her. She even has refused to come to our wedding because I’m a “stranger” since I don’t call, where I had to run over to her house and try to save our marriage as my fiancé said he doesn’t think he can go through with it without his mother being there. She threatened estrangement if he married me.

We are okay now. But all of this still hurts. Mostly because my fiancé is a dog with a tail in between his legs in front of his mother. He tells me privately when we are arguing that he disagrees with his mother about her false perceptions of me, that he knows she’s wrong, he cries that he loves me, that he is willing to cut ties if she refuses him to be with me. But in the moment, when she’s screaming at me, he’s standing there silently and I face her anger alone; usually leaving me in tears. It’s embarrassing and even demoralizing. I would never let my parents treat him in such a way but he, almost 40 years old, is ridden with fear with his mother.