Once the first episode of splitting occurs we are suddenly confronted with a completely different individual and at a loss to understand what is going on. We still initially see them as the person we have a great deal of love and affection for and being the caretakers we are it is not in our nature to leave immediately. As the push/pull cycle begins to unfold though we increasingly being to realize that there is a very significant problem and this is not a phase or an isolated incident. In an effort to understand it all we begin to look for answers, If fortunate, sooner rather late, we can at least identify it as BPD. The initial break by the pwBPD, realization that there is a greater problem, the effort to educate ourselves and figure out it is BPD all take a bit a time. Unfortunately during this period we begin to experience the unfortunate mental/emotional/physical abuse. Armed with a diagnosis and true understanding of the magnitude of the situation many of us chose to create healthy boundaries and/or leave. However the pain and damage that we went through during the time we were simply figuring things out is still there to deal with.
That is EXACTLY how my relationship unfolded - from how I felt to what I did.