You hit it on the head when we said you can't be an enabler to her poor decisions. A little bit of peace can come to us when we accept that it is not within our power to fix them or save them. I have met several people from my BPDex's hometown since we split, and most all of them I have talked to know of her or her family and the reaction is almost the same across the board: "Oh my god, you DATED her? She is CRAZY!". Her reputation and her actions were set in stone long before I ever got my hands on her, and by all accounts she is doing the same stuff now that we have split. Even knowing that though, it doesn't make all of the hurt go away.
I had a couple conversations like this with current friends of my ex, while we were dating. It's a bad sign when your friends aren't feeling it, but when even their friends saying so, RUN.
Mercy is a tough concept because I think it is easily confused with obligation or guilt. And we feel like we're doing the "right thing", as opposed to being twisted into putting ourselves in situations we don't belong in. It's a fine line, and when you're struggling see the truth as opposed to fiction, its easy to miss the line entirely.
What about mercy for yourself? At what point do we have to say that I acknowledge my own mistakes, but I am forgiving myself and getting out of the toxic situation that led me here - and not allowing my feelings of "morality" stop me from doing what I
know is right, even if it doesn't
feel that way right now.