There’s an overlap on that Venn diagram that includes false realities, gaslighting, “it’s not my fault”, and a need for a nemesis (to blame things on). There’s a reason they both exist under cluster B.

The difference is BPD ultimately turns inward and damages themselves through suicide or self harm. Sometimes bordering on outright mutilation of self. Whereas the narcissist never does. It forever remains other people’s fault, for them.