What a beautiful soul you are Atimb; welcome to our caring community.
The best advice I can give you is to take care of yourself first; be the best you can be. If you fall to sympathising too much, it won't serve either of you.
The next thing is to research her diagnosis' to be well informed about her behaviour and their causative factors. This can help you understand and plan ahead on how to respond.
Having a borderline personality disorder (BPD) means she may present as unwilling to accept therapy at times. I won't go into it now, but urge you to explore her disorders for your own piece of mind as an observer; you can't do it for her.
Please stay away from blogs or sites without proper credentials; well known Universities here and abroad are far better for quality, reliable info, and tend to have fact-sheets that satisfy layman terminology. If you feel you can cope with scientific jargon, then please go into it further.
BeyondBlue (this site) have a broad range of info in the links below. And, if you call the mental health hotline in your state, they can provide urgent support or refer you to places/people who might help.
*Any talk of suicide or self harm needs immediate attention. The MH hotline is a good place to go otherwise call 000 for police/ambulance no matter how much she might resist*
The way you respond to your gf will set the stage for your future together. Try not to engage in argumentative to-and-fro's, there'll be times no truth or rational explanation will do. Pandering to her won't work either; this can turn back on you in the long term.
With PTSD, she may exhibit very sad or irrational behaviour due to triggers, either real or perceived. Yeah I know, there's a lot to learn. But coming here as you have, and loving her as you obviously do, can help to overcome any confusion and worry you may have. It just takes patience, courage and commitment.
Things may take a toll on you too. Try to be aware if you begin to show signs of exhaustion, helplessness or anger for instance. You need to be motivated and Mentally Healthy as well; sometimes a break's good.
I wish you all the best Atimb. You sound really caring and intelligent which I'm sure will benefit you both.
Please visit again so we can chat more...hope I've helped.