My partner has many BPD traits. I want to be able to understand her better, to help her, and to improve our relationship.
Hi DanielN2 welcome. I'm something of a Newbie myself and have found the support her very helpful so I hope you find that as well. While I'm not an expert on support of any sort I can share with you a few things I've learned in trying to deal with a (now ex) partner who I believed had BPD traits. In dealing with them (or anyone in general in fact) I found these two resources very helpful:
https://bpdfamily.com/content/listen-with-empathyhttps://bpdfamily.com/content/communication-skills-dont-be-invalidatingI'd also recommend that even if you feel your partner has BPD to not share that 'diagnosis' explicitly or otherwise. Perhaps a few priorities could be:
1) Learning to apply the Empathy/Validation skills regardless of what your partner has or doesn't have. It will help regardless
2) Learning to take objective stock of your own behaviors and see if you could improve your communication/support/validation etc skills so as not to exacerbate any issues
3) Learning what signs to look for that are triggers or signs of BPD so you can learn to deal with them calmly and rationally when they do happen. For myself I did not know/do this and reacted very strongly and made things worse, not better. With a little more knowledge and insights into myself even I could have possibly redirected a situation that spiralled out of control and hurt both of us into something more positive.
4) Learning to set boundaries and protect yourself since, ultimately, you cannot be responsbile for their behavior, treatment or 'cure'. You can only learn to be the best you to them you can and to take care of your own self just as diligently.
Sorry if the input is somewhat generic, it is s summary of what I've learned here and I have to say by learning to step back from the situation and look at both myself and the other person with some dispassion it helped me to understand the situation, the other person,myself and 'us' much more insightfully. While it may be too late for us and might always have been it will no doubt help me in all my future relationships, romantic or not.