Understanding BPD

Hi all, its my first time here. Im not sure how to go about this so please correct me if I am offtopic or in the wrong thread. Basically my loved one struggles with BPD and am trying to understand her actions and thought process to care better (for herself and me). Reading about BPD I have not seen her to be narcisstic or manipulative but instead fearful of abandonment/rejection, has some spontaneous behaviour (eating disorder related), suicidial ideations and issues like a lack of worth etc. I emphatise greatly as she has had a horrible childhood from which the diagnosed BPD stems from and bad romantic relationships prior with really awful guys. I see so much good in her, she is caring, generous and intelligent, great at her job, loves animals and has overcome so much. One of the issues I have experienced is that she seems to find it difficult to accept my love and being in a healthy relationship, almost not believing I am in my right mind to love someone like her, doubting that its real and not seeing the importance of respect in a relationship for herself. She has gone back to her ex who has been emotionally abusive. I just was wondering if anyone has experience or knowledge regarding this - if someone with BPD may tend to choose what is unhealthy due to a poor sense of self? I also had to leave a few months ago to live in another country for the next few years and this I guess has been what really drew her back to her ex, seeing this as abandonment. From what I have experienced together with her and just looking over things to see what makes sense, I do tend to believe (I am a rational person I promise) towards that she wants to me with me but these issues, particularly with abandoment, have made it very hard for her to challenge her BPD in the face of these circumstances. I am not in a direct caretaker role any longer at the moment but do care about her and want to respond in the best way when any opportunity to care for her comes again. Would love to hear anything, thoughts, experiences etc you guys have to share. Thank you for reading this and the ability to write this.