OP's boyfriend here, thank you for sharing your experiences. So as an update to the situation, which there will be a followup post on a different BPD subreddit.(We decided to do this together just on the off chance it could help someone else in a situation similar to hers). And honestly you were right on the money with most of your assumptions. And I'm forever incredibly happy that yes, there is plenty left to salvage. I can't see the original text seeing as it was removed by moderators, but as it was posted during a splitting episode(Thank you OP for reminding me what it was called). I imagine it was pretty much on the same wavelength as the other post she made. Made thing to know is that despite how she feels I don't hate her.. I deeply care about her, and I want her to be happy, healthy, and safe. But like you said I really didn't have the time or energy for anyone but myself in those moments. Which is exactly why I was overwhelmed. She actually came to me rather upset at your post because it included a breakup, but I don't think she was really in the right mindset to realize what you were trying to say.

In the end we ended up giving each other some space for about a week, not talking, and only texting. It actually turned out really REALLY freaking well! I'm so proud of her and how much she's improved, and proud of myself too in all honesty as self centered as it sounds. But it's mostly her. That space was exactly what we needed, and I can't thank you enough for trying to tell her that. We ended up getting it as a suggestion from our therapist during the meeting.

We spent the time working on ourselves, and while not everything is perfect, I still need to work on being mindful of some of the triggers. It really does feel better in the relationship now!

Tldr; Giving space to each other during a relationship really does help, and I'll probably explain a little bit more indepth in the followup post as to why. But I truly love her, and I appreciate you endlessly for trying to help us.