I disagree.
The option is to overwhelm her with kindness. What that looks like to the OP is what he should decide.
I've had my own experience of direct racism from a former friend's father who, plainly said to my face, he didn't like me cos of the colour of my skin. At first, I took offence, but then I decided to just get in his bubble and have a conversation. I did that repeatedly and he came to see me as just a guy, like him, and we got on famously until his death.
For the OP, kindness could just be offering up a 'good morning' or 'how are you doing today?' without stopping too long for a chat if he doesn't want to.
She'll, eventually, shut up, speak with him or somebody else will report her behaviour as maybe she has mental issues. He doesn't need to attack her as she is doing to him.