Many factors contribute DownandOut and an isolated case of invalidation would not cause it no.
Are you able to look at her actions while she was with you rather than dig back to her past. You will be assuming a lot if you try to piece together that puzzle and you will send yourself in knots.
You didn't cause her behaviour - are you trying to find valid causes of her illness because you are self-blaming?
Yes, I guess in a way I feel like I wasn't good enough or, at the very least, didn't try hard enough when that's not 100% true and I know that. She made me feel like I was special and then told me that, although she did feel some type of love for me, it wasn't the way she felt with two other men from her past that she considered herself really in love with. That stung. Therefore, since then I've been trying to piece together whether or not she may actually have BPD, or I just wasn't the guy for her. I prefer the former, because there has to be some validation to how I felt and how she said she felt for me.