Therefore: don’t care about him painting you black. Don’t care about how others think about you. You and your real friends know better. Care about yourself and don’t bother about others, who do not deserve your attention.
I absolutely agree 110% with VeryScared. I've been blacker than black and I've let it wear me down and break me. It's the worst feeling in the world to know that other ppl whom you've tried to be accepted by and belong with are feeling and saying such horrible things about you.
Thing is, you know different. JADE-ing isn't going to help - actually it will, most times, confirm to those who have JADE-d you, that you are what you've been painted as.
Know who you are, be who you are, and be loved by the ones who know you and love you.
Looking for clues into him being with someone else is only going to drive you nuts (been there, done it - regretted it). It opens the door to hurting yourself in the long run more than it will hurt him. If you're doing that for confirmation and closure for yourself, then do it and close the door on it and move on with your own healthy life.
If he is gone with someone else, and she thinks of you as a "pest", you can't change her perception of you. She may need to think that of you to be with him (did he do that to his ex at the beginning of your r/s with him? is this his pattern?)- and he may be using you as a reason to make her insecure which gives him the upper-hand in his new, obviously unhealthy r/s with her. It's not uncommon for pwBPD to paint their ex's black to the new partner (fulfills the "victim" role, less likely to abandon), and use the ex as a means for creating insecurity in the new partner (fulfills their need for neediness in their partner, as well as the knight-in-shining armor that he'll protect her from you).
The best thing to do is let him hang himself with his own words, eventually she'll figure out the truth as will everyone else. Right now everything you say/do in this situation to defend yourself can and will be used against you... .
Work on being healthy and moving forward. It might get worse before it gets better, but keep your sanity and ignore all of it.