First time replying to anything on here. I'm far from an expert and far from in control of what's going on in my own situation, but here's what I can offer.
I'm speaking as one of the lucky ones in a sense. My wife and I had two years of alternating between strolling through a minefield, anything could set us on a path that would have us kneedeep in the mud, slogging through the trenches. A month and a half ago she entered intensive inpatient treatment. I am so immeasurably proud of her.
She's asking to end the marriage, but I suspect that's just her wanting to slough off the shame of her past actions. And just recently, after many moons of study and me watching videos and reading this board, and really examining my role in things, I realized the tools that I had to try to reach her were wholly inadequate. I was trying to open a lock with the wrong key.
Anyway, this isn't about me, it's about you. So let me tell you what I've learned. The first thing is to let go of everything you've gone through already. Your assumptions were wrong from the start and the way you've been trying to solve the problem or get your partner to listen to you or really ingest all the sense you're surely making, is wrong, and likely making the situation worse. Don't let go of your anger, your resentment, your injured past self, realize your part in making it happen. She may be being unreasonable to you, but because you don't understand the real reason why that's happening (you are sick), you are rushing the car down the hill. Not because you're wrong about how you feel, but because of how poorly you've addressed what your partner is going through. You're trying to drive a manual like an automatic, you need to learn to use the clutch.
At the beginning of these arguments, you may be in first gear, drifting to what you hope is a stop sign. Your partner however, is in 5th gear blazing down the highway at 75 miles per hour. What would happen if you just slam her car into first gear without slowing down or pushing in the clutch. You'd rip out your transmission and and blow the engine and everything ends in a fiery ball of misery. What you need to do is slow the car down, and downshift the conflict so that you both are in the same gear before trying to make sense of what's bothering you. This is what pBPDs can't do. It's as if they woke up in this manual transmission car going as fast as it is, they can't remember how they got there, and they've never learned how to drive stick. Imagine how much panic that must cause.
So what's the first step? Where's the clutch? Just listen. And because your partner is likely very perceptive to non-verbal communication, it's not enough to just keep your mouth shut, really be conscience of what she's seeing from you while you're listening. Mirror open posture, keep a positive or concerned look on your face, and just allow them the space to explain to you what's going on in their head, more accurately, what they feel. When you feel the need to interrupt, remember, they've come-to hurtling down the highway at 75 miles an hour at the wheel of a car they don't know how to slowdown. No one can care about how you feel under those circumstances. Any attempt to make them understan, will only work against your goals.
First, ask your SO why they are so upset, and do so with real concern. Then just listen, and really take in how they respond.
When your SO is done Leave at least three or four beats between the last thing they said and you opening your mouth. Then the first thing out of it should be to validate her. I know I know, you want to tell her how little sense she's making, how this isn't a big deal, how you love her and what she's feeling is out of proportion to what's going on, but do. not. do. that. Remind yourself over and over again that her car is out of control.
As far as your SO is concerned, they're going to die, you're mad, you're going to leave them just like everyone else, they are in a state of incapacitating panic. Telling them they don't make sense isn't going to make them feel like you care. Telling them, "Of course you feel that way. Of course that hurt your feelings. I can totally understand why it bugs you when I talk over your favorite part of a movie." Will let them know that you are there, you are present, and you are aware of what's going on with them. You don't have to apologize, but you do have to acknowledge what she is feeling is real, it's all encompassing, it's brutal, and it sucks for her. Most importantly for you, remember, like the car, it is completely out of her control.
I don't know if any of this makes sense, and it certainly doesn't in a normal nBPD/nPBD relationship where both parties can express their feelings with the expectation the other has the capacity to internalize them, but it's the only way I've found to make any progress.
By listening without interruption, and validating the way your SO FEELS, you help slow the car down, get her to the side of the road. Then and only then can you get out of your car and start talking about what happened.
I'm just spitballing here, but I found this piece to be helpful in understanding what it's like to have BPD:
https://bpdfamily.com/message_board/index.php?topic=306200.0And this one helped me understand my role in what was going wrong:
https://bpdfamily.com/message_board/index.php?topic=306200.0
