Except she was saying the cops have been called because she's black and he's white.
She wasn't calling the cop a racist, she was saying that people are racist and are more likely to call the police on her. Which is definitely a truth that people are more likely to call the police on black people.
Now, whether that's why it actually happened, I don't know. I can't blame her or the cop for being oversensitive in this matter, either.