I don’t want to keep doing this. I also don’t want to see her hurting. I think this is a me problem.
This may or may not help, but when my BPD ex suddenly broke up with me, I felt like the world had ended. I couldn't imagine a life outside that relationship since we had been together for so long, raised kids together, etc. So I went through similar patterns, not as bad as what you describe, but the same things over and over. The same arguments and accusations. The same whispers behind my back with sideways glances.
Maybe 6-9 months after the relationship ended, I realized that what I clung onto so tightly was the comfort of our relationship. Sure, it was bad sometimes, but she knew how I liked my coffee, we had the same hobbies, we could finish each other's sentences, etc. Even though the stuff that really mattered wasn't there, I stuck around because it's what I did for 20+ years and it now felt entirely normal.
I'm not trying to say for you to stay or leave here, so please don't take my story as inspiration on what to do. Instead, I just wanted to show that what I thought was a normal relationship in the moment was actually a disaster once I had some distance from it and enough time to process. You can't truly evaluate your own relationship because it feels so darn normal.
If you're unsure, some time apart would do you wonders. I'm not saying to end things or even separate, nothing that drastic. But stepping back even for a short period of time can really open your eyes to what you have and how it completes you as a person. Maybe her occasional rants are normal, maybe they're completely abnormal. I can't say as an outsider looking in. But you can find that answer on your own by putting some distance from the fighting and anger.
One more thing- nobody wins an argument when BPD is involved...absolutely everyone loses 100% of the time. So if you can hold back from exploding or find a different way to avoid the fight, then it goes a really long way to stabilizing the relationship. Likewise, finding different communication patterns is massive since it allows you to discuss sensitive topics without declaring war.
I'll admit, I was lousy at it most of the time, and I got so much better after we separated. Why? For the reasons I just discussed...I saw things from a fresh perspective and recognized the mental illness patterns. I realized that the fighting had nothing at all to do with me and was 100% about disordered thinking with my ex feeling horrible inside. That changed my anger into compassion and the arguing completely stopped naturally.
I hope that helped, I tried to hit "both sides of the fence" there.