You are correct, The video does not show the earlier part of the encounter. Something had been said, and instead of walking away, the black woman escalated the situation and it lead to her physically assaulting the white woman.
I think it does. At the beginning the black woman walks past the white lady and white lady says something to her. Black lady gets triggered and starts to rampage. Which of course she is entitled to do cuz ... slavery and stuff.
(white lady in NJ should have known that would happen)