Wow. You were thrown a lot of guilt-laden accusations. I can imagine all of this de-centering you.
Remember putting a boundary of not JADEing in place is good to try to apply to all relationships, not just those with pwBPD. Although I understand the gut feeling of wanting to respond to the friends and all on FB, it would have been fair enough for you to pause, close the computer, and respond or not respond later when you were feeling more centered. It is like walking away, for you to get re-centered, during a dysregulated exchange with a pwBPD.
https://bpdfamily.com/message_board/index.php?topic=228111.0Also, can you elaborate on your desire to go no contact but her blackmailing you to remain low contact and also remaining in contact with her mother?