We are all terrified of her.
Does she ever get physical in any way, or is it exclusively verbal abuse?
I can understand how hard it has to be for all three of you and I can understand your concern for your daughters. Can you get your daughters into therapy? I'm particularly concerned for your younger daughter, who is painted black.
I commend you for recognizing the problem and for starting to seek help. It won't be easy, but your children will be eternally grateful if you can help them and defend and protect them. Telling them that mom is sick and can't help herself won't help them. They need to be protected from abuse.
Your story is somewhat common, if you read posts on the board for adult children with BPD family members. I've read multiple post by adult children who were the one that was painted black by their BPD mom. Generally, they had a father who was afraid to protect them, which made for a bad relationship with both parents.
I've shut down communication. I'm afraid that what I say will just get me into another argument on why this is all my fault and why I'm causing all the problems.
The two threads below might be helpful and/or give you some ideas. Sounds like you don't JADE (Justify, Argue, Defend, Explain), but that thread could help you with some alternatives to just saying nothing.
DON'T JADE: https://bpdfamily.com/message_board/index.php?topic=139972.0THE DYSFUNCTIONAL DANCE:https://bpdfamily.com/message_board/index.php?topic=66672.0Just a few questions about your wife:1. Has she ever been diagnosed with any mental illness?
2. Has she ever taken antidepressants or meds for anxiety?
3. Are her symptoms getting worse?
4. Has she ever had therapy?
5. Anyone else on her side of the family have mental health issues? (maybe her mom?)
I understand that this has to be very overwhelming for you right now. It would probably be best if you can find a therapist that is familiar with BPD. Going to therapy and posting here can be a good combination. Some people like to post about setting boundaries and ask for help with starting to use some of the communication skills.