this is probably less about mirroring, and more about enmeshment, idealization, and the natural way in which humans that bond tend to rub off on each other.
having said that, a person with BPD lacks a stable sense of self, so it stands to reason that a pwBPD will more easily be 'rubbed off on', and adopt a persona that is more likely to be acceptable.
mirroring is not in and of itself a bad thing, or a uniquely BPD behavior; our mothers mirroring us as infants is crucial to our development.
more here:
https://bpdfamily.com/message_board/index.php?topic=58298.0When I see her talk online, it makes it easier to let go of her. She's the girlfriend now. Not the girl I loved. The person she is now isn't someone I'd be attracted to. At all.
so who was she when you were attracted to her? why were you attracted to her?