Hi Captain Jay,
I'd suggest to read as much as you can about the disorder and understand that she has limitations, she can't meet you halfway in the r/s, you haved to meet her at her level. Learn to become indifferent to her behaviors, depersonalize them, what she's going through is not personal to you, that is why reading about why she acts the way that she does is so important. That being said.
I can understand wanting to validate your feelings, she might be able to do that slightly from time to time, it's probably rare, i'd suggest to share that people that can relate that, namely us, it helps to validate your feelings.
A pwBPD need a lot of validation, invalidation is very painful to someone that is highly sensitive, she feels low self worth, self esteem, self loaths and self hates. I'm not saying to validate the invalidate but find what is valid, everyone wants to be heard, feelings equals facts o a pwBPD, it's really important to validate first and just communicate differently, and package your truth at the end.
Communicate - S.E.T. (Support, Empathy and Truth)