Hi Flyguy 2121,
She sounds like a classic BPD, and the fact that she can't trust is a trait.
She never trusted me. Saying that my “past that she had herd of before we dated” made her believe I couldn’t only be with one woman.
It is difficult to trust others, when one doesn't trust themselves. This is the predicament of loving a pwBPD. It's a push/pull romance, and if you haven't, I urge you to read "Stop walking on eggshells". There are many good resources for you to bulk up on listed on this site. Having this knowledge will help you when you need it.
It's understandable that you love her. Love just doesn't turn on and off, except for those with BPD. My husband goes through cycles of love/hate. Four years ago, I stood in a similar position. He left and was accusing me of all kinds of things, including my past before I met him. I knew that in order to recover, I needed to first take care of myself. That's when I made a tough decision; give up, or give in. I wasn't ready to give up, but I also didn't want to be discarded over and over again. The hurt is incredible. When he finally did sit down with me to have a conversation, I let him know that I was ready to let go. The crazy part of BPD is that emotions rule their decisions. He let down his 'guard' and we managed to make decide to work on our marriage. I'd read books and gotten help from this forum. Without that, I don't think it would have happened. Validation is an important tool, as you mentioned. We all like to feel as though we are being heard. When you said,
I would say please take your walls down.
unfortunately, she doesn't realize that she has walls. The walls are mistrust.
I'm so sorry that you are feeling empty

Take this time, to look inside of yourself. Go to the gym, eat healthy and see your friends. She will respond better if she thinks that you are moving on, as that may not be what she wants at all. If you are depressed and 'needy', it will be seen as a weakness. Hold your head high, and value yourself. I'm a bit of a romantic that believes that love can conquer all, in most cases. Loving someone with BPD takes stamina and determination. It's been a rocky five year marriage for me, and always will be. It's possible to adjust to the moods and outbursts, and the main ingredient is change within yourself.
You did as much as you could with the information you had. Now, you have new hope and a whole new family that understands.