It is astounding that she didn't stop herself when she looked in the mirror at herself doing black-face. I wonder how much American history is required to obtain a degree in law. Apparently, not enough. We've seen (and lamented) how Trump's racist cartoonishness has had an effect on less educated white people but I guess this would be an example of how it affects educated upper-middle class whites. She didn't intend to denigrate anyone, rather the opposite, but this incident demonstrates how many white people just don't have a clue, even after they read a book detailing racism. 
It was arrogance on her part to think that just because she read a book detailing racism and was fired up about it that that somehow gave her permission to reproduce and re-enact the black-face tradition that mocks and derides African-Americans.
How could she think no one would take a photograph of her? How could she not consider this possibility? She was astoundingly stupid.