I don't think she's racist, it was obviously a mistake. Though, I will say I can completely understand why someone would be offended. The idea that all minority people are the same and we always get lumped into one group still runs rampant, whether she meant it or not. Aside from both having the letter F in their names, "Hidden Figures" and "Fences" don't sound anything like each other, and I'm pretty sure these people wouldn't have confused two predominantly white-casted movies, but....
The creatives behind each of those films deserves much more respect than that, and I'm glad she apologized.