By BPD, I assume that you mean Borderline personality disorder. Since extremes and mood swings, and instability of interpersonal relations are hallmarks of BPD. I would expect the opposite-trying to engage you, embracing, loving behavior, and smothering. I am going to include a link that describes the symptoms of BPD so you can know what to expect. The important thing is to try to react with your head (rationality), not your heart (emotionality). You may unconditionally loving of her as a person while still disapproving of her behavior. When you express it (disapproval) do it in the most non emotional means as possible as you do not wish to reinforce the inappropriate behavior. I hope this information has been useful to you and I wish you the best.
If you require further clarification or more information, feel free to ask!
Please click the green "ACCEPT" button on this page if you are satisfied with my answer so that I get credit for my work. Your positive feedback is most important and bonuses are always welcomed. If this is a mental health, or medical emergency, please call emergency services (911 in the USA), or go to your nearest Emergency Room. The opinion provided does not replace an evaluation by an appropriate professional. Use of this website DOES NOT CREATE a provider-client relation and this information is for educational purposes only.