(FYI, you might get better response in
https://bpdfamily.com/message_board/index.php?board=7.0 which is technically the board for parent-with-BPD, not a big problem)
The hateful text/email messages are so incredibly toxic, and a function of the modern world...but I know the solution!
I actually solved the problem back around 2011 by insisting that I didn't want emails or texts from that specific dBPD - and we could communicate by snail mail. She ended up writing me letters almost every day, but even the ones that started off toxic usually worked their way quickly around to more healthful topics - it took me less time to write her a few letters every week than I otherwise spent dealing with insane text messages threatening to kill herself, kill me, ruin me, ruin her co-workers, etc. It's also when I learned she has a...childlike side, since the letters would come covered in Sandylion stickers, glitter glue, gel pens, etc. It made the toxicity of keeping her in my life more tolerable to remember that ultimately she was still just a scared, anxious (destructive and dishonest) little girl in many ways who had never overcome childhood trauma.