My partner's Mother verbally abuses her Father. Did I mess up by confronting her?

I've been with my partner 5 years but we are not married. Like most, our relationship is rocky but over the past year we've really been struggling. Today I got into a confrontation with her mother (we'll just say MIL) while her parents were visiting for the weekend. MIL left very angry at me and as a result, my partner wont talk to me. I'd like opinions on how I should approach this conversation with my girlfriend when she is ready to talk. Did I step out of line with her mother?

Her parents are very unhappy with each other (no physical contact, sleep in different rooms, don't wear wedding bands, etc.) but whatever, it's not my place to judge and both have always been very kind to me. Problem is that MIL is really verbally abusive to her husband. Never threatening to hurt him (as far as I know) but repeatedly calling him "stupid", talking to him like he's a child, spelling out words to him, yelling, telling him to stop f*cking eating, and generally being demeaning. This happens 10-15 times a day every time we see them. FIL never get's angry or yells back (although my girlfriend has told me he does when I'm not around) but tells her to calm down, stop, rolls his eyes, or stonewalls if it gets really bad.

Serious anger issues. MIL once missed a highway exit and started raging to the point where I felt unsafe in the car. But when we get out of the car and she acts like nothing happened. My girlfriend is always embarrassed by her mothers behavior and will apologize to me after. We've talked about it, I've told her it's abusive to her father and I hate being around it, but she defends her mother to the end. Apparently MIL was terribly abused as a child and has had a tough life. My girlfriend has severe anxiety issues herself and I think her mothers rage is where it stems from. Apparently once a psychologist told MIL that her anger fits were impacting her children and after that, MIL made a suicide attempt. My partner told me that I can never confront her mother about it because she is afraid she will try something like this again. So every time we visit I am just expected to ignore the abuse which is impossible.

So to today, FIL and I were trying our hand at baking a pie in the kitchen. MIL and my partner kept butting in and telling us how to do it. We told them to go outside for a walk and that we would figure it out. They stayed and MIL kept yelling at FIL that he was doing it wrong, and making him feel dumb... and making me feel dumb. This really started to anger me and eventually I snapped and yelled 'Can you just leave us alone please!' After that she went upstairs packed everything up and started loading the car. My partner got angry at me, told me I was extremely disrespectful and defended her mom. As they were leaving I asked her mom to sit down with me so we could try to work it out but that only made things worse.

She said that I stabbed her in the heart and "didn't know I was just pretending to like her all this time." I told her that I was tired of hearing her degrade her husband around me, and that by doing so constantly she was degrading me. That when I visit her home she can do and say whatever she wants, but she was in my home and I didn't want to hear it anymore. Also, that it didn't f*cking matter if the pie turned out good or terrible. I apologized for hurting her feelings but I was fed up. MIL didn't believe my apology was sincere and said she would never have spoken to me that way. I told her that everyone else in her family yells at each other so why am I not allowed to? Her response was that I haven't been in the family long enough, that maybe one day we'd be able to repair our relationship but it would be years.

Her dad kept apologizing to everyone and eventually they left. My girlfriend has refused to talk to me about it since. Should I apologize even though I feel like i'm the one who disserves an apology? I do feel some guilt because I don't want MIL to hurt herself but at the same time, I think is a serious problem that everyone else just seems to ignore the abuse. Sometimes my girlfriend will even join in with her mother in degrading her dad. This is a big red flag (when thinking about my future with her) but she says it's just her family dynamic and that I don't understand because I wasn't brought up on the east-coast. To me it's toxic and i feel like when we visit, it impacts our relationship. Am I in the wrong here? Am I just soft to this behavior as a westerner?

Any advise on how i should try to talk to my partner?

Well, you correctly identified it. The mother is extremely abusive which results in her being able to control and manipulate everyone around. Since everyone is afraid to stand up to her for fear she will commit suicide, her abuse has evolved to the point that it's one of the most extreme cases I have ever heard about, particularly since she has her daughter defending her outrageous behavior and the father no longer fighting it. I don't know if the mother's behavior can be changed at this point. I think she's severely mentally ill.

Fighting back against her just causes the type of behavior you saw. In this case, her weapon against you is her daughter. She played her trump card against you. Now if everyone just ignored her, she would have no power over anyone, so she would have to escalate things by threatening suicide etc. It's too bad that the father didn't call medical services the first time she threatened suicide. She might have been committed to a psych hospital and gotten therapy. Now, she's been left untreated for decades and she is a horror show.

In short, I think this relationship is totally screwed. If I were you, I would keep well away from the parents and have nothing to do with the mother.

What you have to say to your girlfriend is that you didn't know her mother was so sick. That you will never snap at her mother again. And you're very sorry. If you do have to deal with the mother again, you have to keep your cool. And you almost have to play a game with her. If she calls you stupid, you have to ask her, why did you call me stupid? You have to question everything she says without getting angry. This will cause her to have to think about what she's raging about. Of course, it might enrage her more, so you have to know when to retreat from this strategy. But you might get the mother to at least stay away from you if you question everything she says. You can read more about this strategy online if you Google how to deal with emotionally abusive people.

You said you're having other problems with the relationship. Her mother be the deal breaker, but that is up to you.