A question to black native (US) English speakers from a French mostly-white fluent ESL speaker

[pauamma]

I came across https://verysmartbrothas.theroot.com/thoughts-on-forgiving-amy-cooper-aka-darth-karen-who-1843701476 on Twitter, and I'm curious about a linguistic detail of it: in 2 places(*), it seems to use the n-word to refer to her, even though in the still shots I saw she appears to be very white. Is that common usage? I seldom see that word in writing in any of its variants, but I don't think I ever saw it used it to refer to a white person.

(*): adjacent to "YOU HAVE LESS CLOUT THAN A BAT" and to "MIGHT GET BANNED FROM CENTRAL PARK".