Hello,and thank for reading this.I recently broke up with my ex who has BPD.Twice I’ve been cheated on, and decided there won’t be a third time.My first dance with the uBPD/NPDexgf was exactly like that. I went NC [except to recover my personal belonging and a vehicle that I paid for].
The most heartbreaking part is she hasn’t even tried to contact her daughter or try to understand why she left.I was blamed for her daughter leaving by the ex,I had nothing to do with it. The ex needs to take responsibility for her daughter’s trauma and emotional abuse over the years.What kind of parent does this to a child? Who would ever ignore their child in their hour of need?An emotionally dysregulated and dysfunctional ones - just as she had no feelings for you when she cheated, there is a similar mechanism going on for her daughter too, sounds more NPD than BPD, even though both can coexist.
How do help her daughter?I talk to her daughter every day and will stand by her because I adore her and will help her emotionally and financially.I just started paying for her daughters therapist.Has anyone else had a similar situation?You are helping in a very good way. However, I am going to recommend

as you can become emotionally attached to her daughter in potentially emotionally unhealthy ways.
My situation occurred in the late 1990's similar to yours. The kids did not have cell phones in those days. So, I did go NC after some financial support.
Do self-care, get yourself into individual therapy, to sort out your own emotions.
Also, ask questions here. Vent. Do what is best for you, as only you can take care of you.