I just watched the video, and that White piece of trash was clearly wrong. He had no right to approach her, yelling with a threat, then immediately calling her crazy when she calmly defended herself. Then when she finally starts defending herself in the same tone he's been using, he starts using profanity, then tells her "f**k you", while getting all up in her face. That's where she lost it
This wasn't a case of her going back in forth with him, but more of a case of her defending herself, since he was on the attack from the beginning. All she was doing was calmly explaining she wasn't speeding, and that her company would prove it if she was. Now if she said something like, "there's nothing I can do about my speed, and maybe you're over-responding, etc..." then that would be escalating it. In this case, it looks more like she was tryna deescalate it, but he wouldn't let her.
Although there may have been a better way she could have handled it at the end, I think she held back long enough. At this point, whether she was right or wrong, is no longer relevant. It shouldn't even be a question, since again, he was acting way more dangerous than she was from the beginning.