Hi Scorpio,
no it is not too late but then maybe it is too early to commit yourself to a person who is unstable. Living with a person with BPD is a commitment to being the stable anchor and accepting the ship tied to it jumps about all the time .
It kills me to see her like that and she really has no other support system really hope somebody can help!
If she is convinced it is BPD then she should seek out therapy. You can't be her therapist and her partner - these roles are mutually exclusive. She has lots of issues in her life (some probably a reflection of her BPD) and seeking help is the smart thing and there is no shame to it.
during the arguments she would explain some of her triggers I didn't catch or understanding them fully. Now she feels like I didn't try. I take full responsibility for it being my fault,
It is virtually impossible to avoid triggering a pwBPD. Trying to do so often leads to walking on eggshells, becoming more reactive to their emotional instability. Having said this learning about validation and how to avoid invalidation (even more important) is helping a lot to avoid triggering and making the pwBPD less trigger happy.

,
a0