My mother did the same thing to me, humiliating me in front of friends and family, even talking about me and warning my friends about the kind of person I was and how they needed to be careful.
Any time an adult (teacher, friend's mom, neighbor, etc.) complimented me on being a good kid, my uBPDM would be right there to say something like, "HA! You don't know how she REALLY is... ." and go on a mini smear campaign with me standing there, staring at the floor as these people I liked and respected were told how I was a crazy, defiant, disrespectful, stupid, miserable wretch. She especially liked to talk about times where I "lost it," conveniently leaving out the hours-long sessions of badgering from her that preceded it.
When I finally caught on to this, I made a concerted effort to keep my non-family relationships away from her. I was then accused of being "secretive". I also made a concerted effort to hide any and all feelings. I was then "cold" and "hateful."
Ultimately, I went NC. It took a lot of time and work to stop believing her version of me, and see myself for who I really am.