I found the exact opposite, she would always say she does not hold grudges but then would bring up some mistake or manufactured mistake I had made in the past to throw in my face.
She would not hold grudges against herself though, it did not matter how nasty she was, she was always willing to forgive (herself) and forget.
Having done some googling, it seems alot of pwBPD do hold grudges, and now you say yours bought up things from the past, mine did too, and it used to catch me of guard how good her memory was.