One day I came to her house in the evening and as I came in through the screen door and looked at her on the couch it was as if the veil had dropped somehow and I saw a different person sitting there than the one in my mind. She looked at me for a second too as if she could sense I saw "the stranger" and began talking smoothly and saying things that reassured me it was actually her, not some shape-shifting monster.
Now this may be far afield, but I wonder if there were ever moments that you saw a different person completely and wondered "Who is this, really?"
I can totally relate to and agree with the general idea that there are "different fronts"... like the mask can work with friends and the work environment, and the real punishment can be reserved for lovers/family, depending on what is going on in the BPD mind.
Personally, I think I've stopped asking myself whether or how my ex was 2-3 people, who knows about the diagnosis or destructive behaviours, although of course I still think about it. I just think it's a no-win because the clever, high-functioning ones are able to hide it, not forever, but that's exactly why they would leave, in my opinion.. being "found out" is a source of shame.
Also, to answer your question - yes. For me, the moment when I saw the "other part" of my ex is when she uncharacteristically and completely out of blue tried to assault me. Sadly, I was triggered by this at the time to recognize that is was "her" doing it. But I think it's very important in relation to personality disorders, or any kind of compulsive, traumatic behaviour, to see the "whole" person... not to push aside moments when they act "out of character". That's something I've learnt now.