Since "diversity" is usually aimed at darker skinned folk I will answer your point on that. Not all blacks look alike, nor are their features all so pronounced. You can do a quick image search and see this, especially so in America where she is from, if I recall. The big complaint is people claim they always make them ugly or choose ugly actors for the diversity rolls. Having her from the U.S. gives you a lot of leeway as far as the appearance of people goes from all of the racial mixing that has happened.
As far as stereotyping goes, they exist for a reason, as these girls were always (for the most part) pretty bad people to begin with. This went with the character progression you had in mind for them in which Yolanda would go from a wannabe thug to a college educated chemist. The reason I suggest toggles, or in this case routes, is so people that like the extremity will be happy and people who don't will also be satisfied.