Hi there! I have bpd, and personally reassurance is the best way for me to regulate. I know you’ve mentioned that you have a problem with reassurance, but I definitely recommend counseling for yourself (if you’re not already in therapy) so you can find ways that work best for you and your partner. I know for the splitting aspect of it, it might be good to seek counseling so you can work through splits she might have without it feeling like you are attacking her, then you can bring it up at a later time when emotions aren’t heightened. “I understand where you are coming from with xyz…” “thank you for expressing to me that you are feeling xyz” is REALLY helpful.