I've decided that I won't be making use of her services because she is racist.
Again, I see no reason to believe she is racist. It's a fact that a large percentage of the violent crime committed against SP's is committed by blacks. She's protecting herself. In a safer environment, say, if she was able to hire security, then she may have no trouble with black clients--I don't know, and I bet you don't know either. The problem for her is that in the current environment, where she works on her own, she cannot tell the difference between the majority of black clients who are law abiding, and the minority who are going to beat and rob her. While for you the question may be academic, for her it is a physical, bloody reality.
And yes, she is MUCH more likely to be beaten and robbed by a black client, than by any other racial group.
We can debate why that is--poverty, racist factors that exclude black youths, lack of strong father figures, immigration from one particular country, take your pick. But it's a fact, and if she wants to reduce the chances that she will be beaten and robbed her choice is intelligent.