After being in two bpd relationships all i can say is the biggest concept that i learned about is called "enmeshment". It's the ability for a person to merge psychologically with another to the point where they can't see the difference between themselves and the other person. So I now realize that I grew up with a bpd mom and when i'm around her it can be so intense because she is such an anxious person that she judges everything that people do. So when I am around her she has me under a microscope and if anything seems out of place she quickly judges it and me because she feels i am a reflection of her. She can't see that i'm a separate person that has different ways of operating. She gets stressed if i'm not perfect and she can't control me.
So I'm still learning about this but subconsciously i sort've attracted women like her because it was familiar. The crazy thing is that in the beginning the female partners that i have had start out so uplifting and loving. It's the exact opposite of the devaluing i go through with my mom. So i liked it, craved it. But what i didn't realize (and now what i see on the boards all the time) is that us non's can enmesh the opposite way. We project our love onto a partner; the love that we want to receive or expect to receive. I'm not sure if this adds to the bpd dynamic because they feel so unlovable and we "overlove" them or project our love on them. (i'm making generalized observations so if this doesn't resonate with anyone please forgive me and only take what does).
Anyway, as far as getting her back? I think first i would say get yourself back. Realize that the love you gave her wasn't lost and you're not empty now. She might have run away with that love but realizing that there is an endless supply is what helps me. I had to realize that i'm a loving person so i will have more love to give. But because bpds are afraid of abandonment, they project that onto the nons when they leave. In a sense, we are feeling the abandonment that they were unwilling or incapable of feeling. They escaped it by pushing their partner away and now we are the ones thinking "well i was this and i was that and yet she still left or he still left so i must have screwed up"
You see what happens? we wind up taking too much responsibility whereas they don't take enough. There needs to be balance if healing is to occur. As nons and many times codependent we need to realize it's not our responsibility to heal another person (as much as we want them to heal because we love them). This is the first step in your own healing. And then and only then if she comes back can you decide if you're strong enough to deal with the ups/downs. But breaking the enmeshment means you realize that you can mourn for the loss of them without thinking they purposefully abandoned you. The only similar feeling to when a bpd leaves a partner i believe is when a loved one commits suicide. In normal death, humans don't take responsibility for someone dying but they go through the grieving process. In suicides the brain can't comprehend why this happened and why the loved one would do this- so it feels like abandonment. With bpd i believe that its sort of like this; we can't understand why someone would leave when we felt so deeply connected with them at times. Because lets face it; during the good times most of us would say that we have never felt more loved but during the pull away, it feels like they killed the relationship with no good reason (relationship suicide).
Will she come back? many times they do- the bigger question is if she does will you be in a place to either handle it and her and be ready for the roller coaster ride or will you be in a place where you choose something different ? only time and you will be able to answer those questions but in the short run my experience (not advise) says that i had to address the enmeshment and figure out what was mine and what was hers. I had to take inventory of who i was and what value i have as a person even though she's not here anymore. Also, most younger cases of this dynamic don't know how damaging things can get once you have kids with a bpd who doesn't get help. So another helpful thing for me was to pretend she already came back. Are you only willing to imagine the good if she came back or can you look at the possibilities of what negatives can happen to you as well? These are things that helped me as i went through therapy etc.