Just have to find my way I guess
You are finding your way ascaffo, you're here and you're talking about what's going on for you; that's finding your way.
I can relate exactly to what you're experiencing and it is painful, I understand.
We all want to help the people we care about, and it feels good when that help and caring is acknowledged. Narcissism is healthy and required to a certain extent, it's when it gets extreme that it's a problem. Think about it: narcissism is self-love, the opposite of which is no self love or self hate; which is better? Of course it's on a continuum, just like the traits of BPD.
Have you learned much about the disorder? There are lots of resources here, and one thing that jumped out for me is you say she was 'just your type in every way'. Borderlines, which their survival-based need to attach to someone to feel whole, will be whoever they need to be to affect that attachment, yes, but also to assume the 'good' they see in someone to counteract the 'bad' they see in themselves; the trait is called mirroring.  :)oes any of that speak to you, now that you know her well? Is it possible what you saw in her that you liked was the good in you being reflected back to you?
You say that you would go back in a heartbeat, to someone who 'destroyed' you and whom you went through 'an extremely rough three month period' with, leaving you depressed and lost. I understand the internal conflict, and objectively that doesn't make sense, why would we do that to ourselves? More will be revealed as you get time and distance.
We could talk about the difference between a loving partnership of equals and rescuing someone you care about who needs it, although for now have you made a list? Try making a list of all the unacceptable things you tolerated in the relationship, all the behaviors; the list will grow as you remember things, and it can be used to adjust your focus as you address the internal conflict.
Hey, it gets better, one foot in front of the other. What's the first thing on that list?