How do you co-parent and remain detached?
This takes time. And a very conscious decision from both people. I was not a good husband (and she was not a good wife), but somehow my ex-wife and I are both great ex's for the good of our kiddo. Occasionally, we will share some tidbit from the past and that is natural as we have grown our relationship to some happy medium of caring for each other with thick boundaries. Mostly though, we know that maintaining a friendship and caring for our kiddo as a team has been really good for our kiddo. Kiddo does not struggle with the issues I did from my divorced parents who were always at war. Be patient though. It takes time to build that trust for that co-parenting relationship
My ex-wife is not the pwBPD that brought me to this site. My ex-wife is a very different person than my ex-GF pwBPD. I am not sure how co-parenting would be with my ex-GF. I would hope it would be the same, but who knows!