Thanks for filling us in. I bet the quiet does feel good.
I have the same question as EyesUp:
How did you answer those questions?
Especially this one:
My 11 year-old:
“Mom said you changed; you’re not the man she married. She said you changed when I was born. She wanted to have me and you didn’t.”
A big mindset shift will be away from defending yourself and towards focusing on how your child is feeling when saying that stuff.
We can walk you through that approach.
...
She hasn’t said one thing grounded in the here and now. Nothing about kids, clothes, pets, bills, divorce, nothing. I told her she has to get off my business’ phone plan and get her own. She is beside herself over that. She can’t believe it. To her it’s the worst affront she’s ever suffered. “Why are you punishing me this way? Why are you being so cruel?”
Given that you're here because you suspect she has BPD, a real mental illness, it may be helpful to pivot away from the shock/frustration/etc when she isn't in touch with reality, and towards
expecting the disconnect with reality. Moving away from "I can't believe she's doing the BPD stuff
again" and towards "Well, I'm not surprised she isn't in touch with reality... now, how can I move forward effectively" will preserve your energy for what matters -- your kids -- and stop you from expending it on what you can't change -- her mental health.
Instead of "asking and waiting" for her cooperation about her initiating getting off the business phone plan... how about "deciding and informing" that you will remove her from the plan by Day/Date?
Waiting for cooperation (rationality) from a pwBPD during a high stress situation... expecting that to work is a "you problem", not a "her problem", if that makes sense.
...
Is there any language in the custody agreement about how the parents will communicate (i.e., text, call, email, app...)?