I'm honestly not trying to dismiss your feelings or experiences. How could I? I don't know you or what you've been through either.
Recognising that all humans have a tendency to tell ourselves negative stories, and that black people, especially, are encouraged to focus on those negative stories, is not a claim that racism doesn't exist or is always exaggerated. I'm betting you could ask any black person at random and they could tell you a story about an interaction that was undeniably racist.
I could certainly tell a few.
But again, my point here is that there are many times when we simply can't tell when it IS racism. No matter how confident we might be.
And given that, as I say in the article, there was nothing this white woman could have said or done to help this lady think otherwise (what's she going to say? "I'm not being racist, I have black friends"?), it's important to take a careful, objective-as-possible look at ourselves and especially the stories we tell ourselves.
And to be clear, it's not important for me. I don't suffer in any way because that woman believed herself to be the victim of racism when she wasn't. Only she and her daughter suffer. And as you say, there's a cost to our health, mental and physical, for being too quick to telll ourselves that story.
That's all I'm saying. If you genuinely don't believe you're ever too quick to do that, this article isn't directed at you. If you think you might be, I'm suggesting, with love, that you think about that.