Given her stance on police brutality against black people and seeing her videos, what likely happened is she got stopped and gave the cop a little too much mouth. Maybe
the cop was rude to start off, maybe . Who knows...
They probably eventually told her to then step out of the vehicle and she refused to without good reason. When she refused they forced her out physically, then took her to the ground in the same fashion.
At that point she's gonna get arrested for their trouble and they can drum up whatever charge they want as an excuse.
After that she likely was vocal about going to jail for a simple traffic violation.
And a black person too smart for their own good is no good when Ur dealing with racist ppl who mentally still live in the 1940's.