Yes... .this is getting better! Keep it up.
A few coaching points.
It seems like it was obvious she was "ready to go" and you were trying to catch up... .
"Hey... .can you slow down a bit? This conversation is important to me... .I want to get it right" (yes... ignore insults and such at this point.)
follow with...
"Hey babe... .what is the one main thing you want me to understand right now?"
I'm a little reluctant to advise you to attempt validation... .because many times when a pwBPD is already "ramped up"... validation comes across as insulting or patronizing.
OK... .so... if this doesn't work and it's time to leave the conversation.
"I need to leave the conversation to sort out my thoughts. I'll check back in with you in 10 minutes to see if we can continue."
Big picture: Yes I think boundaries worked. I also think she had some fear of abandonment going on and she realized you would make good on your threats to leave. (yes... informed speculation on my part)
I would hope you can get away from "if you do x... .I will do y". Sometimes it can be like waving a red cape at a bull (think bull fighting)... .in your case it seems to have worked. So... .use it sparingly... .be ready for it not to work.
You are getting the hang of this... .keep it up.
FF