You are quite right about American institutional racism, but Maria in this instance is a poor example. Her drug problem is all tangled up in her normal meds. Moreover I know of no example of her being an overt racist.
Now having said this, every human is a racist to one degree or the other. It is the natural negative offset of tribalism — those like me are good and those unlike me are evil. It take a bit of sophistication to rise above this hardwired negative offset of the “other.” Indeed, it is fairly easy to gain cooperation from likes and to initiate conflict between opposites — a massive universal flaw as seen from our more enlightened human perspective.