does the BPD know what they did was wrong but can't openly admit it
I have read that in heightened mood states, people with BPD do not necessarily have access to the kinds of cognitive processes that they might when in a less aroused state.
If you think about it, we aren't great at problem solving when we're terrified, either.
However, we tend to have less intense and volatile mood states. And what triggers us may be more or less based on fact, instead of emotion.
People with BPD may be in fight or flight states over things that seem relatively innocuous to us, doing anything and everything to protect threats to themselves.
Their sense of self tends to be extremely fragile and not entirely whole, so it takes less to create these feelings of fear than it might with someone who has an intact sense of self.
In other words, it becomes more important to her survival to defend herself in that moment than it does to corroborate something she did or said 10 days earlier.
People with BPD are individuals, so there is a range of behaviors to take into account. My N/BPDx was seemingly incapable of being culpable. It was like he had to win. Whereas my SO's BPDxw is capable of taking responsibility.
I try to imagine a time when I felt intense shame, and then magnify that by a thousand. Then assume my ex felt that way most of the time.
It's sad.