I just realized after I wrote this that if I contact her, it will re-enforce that she doesn't have to be responsible for her actions. This is why she does the same thing over and over to me because I don't follow through with the consequences for her bad behavior. And we will continue this dance. I just wished it could be different. I loved her the best I knew how with what I knew.
Right. If there was nothing wrong with the position you took initially, following through with it truly is a gift to the other person as well as yourself. It is very confusing to people in general and especially pwBPD to feel like people are messing with and manipulating them, which is what boundaries are that we go back on when it doesn't turn out like we wanted.
Bluffing sucks. Sometimes changing one's mind is necessary of course, if you really think you were wrong. But leaving, then saying "oh well actually, since you didn't change in the way I wanted you to, I'll come back on the terms you originally offered," both reinforces that there will be no consequences to the original behavior, and makes the pwBPD feel like you don't mean what you say.
I have enforced some boundaries that seemingly mean my ex wBPD is gone. It's his choice. I'm sad about it. I wish he chose differently or had the capacity to do so. But that doesn't mean my boundary was wrong. The sadness sends me signals that it was wrong, which feels like what you are going through to; and getting clarity on that has been quite a struggle. Your second post here shows a level of insight that it took me quite a while to arrive at.