There are black people everywhere in middle and south america. Also all over the world a lot of mix people of black-hispanic, black-indian, black-white, black-chinese and so on.
My mother is a mix of black-hispanic-indonesian/pacific islander. I´m a mix of all that and white. So it is posible that those two girls are mexicans with black heritage.
Also if a black person lets say african born in mexico, what do you call her? A mexican right? The same as a black african born in USA, she will be american.
Sorry Anita but I find your statement about those two girls being black mexican or not out of line.
Jessie