The concept of a 'rare beauty' is a backhanded compliment, and in this case, outright reinforces white standards of beauty. Her beauty being qualified echoes the old 'black but beautiful' and 'exotic beauty' rhetoric.
Also, rare to whom? From Togo to Tobago, Haiti to Ethiopia, one can find many people who look like Khoudia Diop.
This is a form of racial micro-aggression that ‘celebrates’ blackness while directly attacking it.
Lastly, is it her 'rarity' that makes her beautiful? Will she still be beautiful in a group of people equally melanated?
"'She's a rare beauty that we had to have in our campaign.'"http://www.dailymail.co.uk/femail/article-3860088/Stunning-black-model-labeled-darky-daughter-night-racist-bullies-tells-overcame-hatred-Instagram-star-rising-fashion-sensation.html