Hi trying2coparent,
I had an almost similar situation around the ADHD medication thing.
What BPD mom wants to do is get the kids to focus on the ball. You need to help the kids focus on the game, which is about helping them use their emotional instincts to detect BS. There are probably better ways to say it
"That must feel bad when mom says I want to drug you. Do you think she knows how it makes you feel?"
"How did you feel when mom said that? If someone said that to me, I think I would feel bad. Maybe even mad."
I had to do that with S13, but I admit it's very hard to do, although I've gotten a lot better at it. My reflex was to defend myself because I felt like I was in a battle with N/BPDx. Fortunately, detachment happened at some point and it got easier to see him as a pathetic, seriously ill and damaged man. If you get into a defensive crouch every time your ex tells the kids something inappropriate, that just makes kids feel like they have two adults who are doing the same thing -- worrying about their own place in the universe instead of the kids.
My son stopped talking to me about what his dad said, which is actually very toxic to kids. I wish I understand the whole validation thing earlier. I think by not talking about stuff with his dad, or saying things like, "That's a grown-up conversation that you don't need to worry about" made things worse.
Encourage them to talk about things -- if they bring it up, it means they're worried. They want validation for their feelings more than anything. After they've been heard, and feel that you're there, you can correct the BS later. Try to not do it right away. Even wait a few days. "Remember how we were talking about medication? For some kids, it's like putting on eye glasses and being able to see if they don't have good vision. I don't know if that might help you or not. But I will feel bad if you go through life not being able to focus, and it's because I don't try and help you." Or whatever you want to say.
