Technically, she cannot defend herself: she is past that point once she is being called a "Karen" and she is being filmed. There was no other course of action than to lay down on the ground in a fetal position, try to hide her face as best as she could, and then hope that her employer and friends would not see the viral video, so that she would not get fired, left by all her acquaintances, and forced to move to another city or state.
She gets it right at the end of the video, but that is what she should have done right away.