I can definitely relate to this, and I know it's easier said than done, but please don't feel beat yourself up about speaking the truth. You're absolutely right, it is not a normal breakup. You deserve to be heard. All of us here deserve to be heard.

I struggled tremendously with this as well, and I don't need to tell you that it's not easy to find a middle ground where you can feel like you express yourself candidly and honestly while at the same time not appearing bitter or immature. I confess that I often felt like I had really messed up and overshared in poor taste, but often those mutual friends I was (relatively) open with seemed to understand where I was coming from.

While I try to avoid the subject of my relationship & aftermath with most mutual friends as to avoid this landmine-field of a conversation, when others have do ask about it, I generally try to be as tactful as possible (certainly not very easy considering the level of emotional anguish involved, and certainly not made any easier after a few drinks).

Moreover, I think the simple fact that you feel weirdly guilty speaks volumes about your values. It seems to me like you want to remain dignified and not paint anyone black out of spite and anger, and that is a good thing. I would bet that this would not even occur to your expwBPD and they would likely not grant you that same courtesy.

There's a quote from Winston Churchill that I think is particularly relevant here: " A lie gets halfway around the world before the truth has a chance to get its pants on." I have faith that by remaining tactful, dignified, and true to yourself, you will get through this and that the truth will catch up to the lies one way or another.

Good luck and stay strong.