People need to realize that you can't use African to describe her heritage.
Even though Benoni is a craphole, she still had a better life than 90% of other Africans as a white South African. Her life experiences are completely different than most Africans.
As a South African she also grew up watching American soaps and television, eating hamburgers and KFC. Her family probably had a maid and gardener.
Somebody like Chelsea Davy, white with a lot of money, they live in a complete bubble. They might be born on the African continent but their lives are nothing like the Africans who don't have the resources they have.
The nationality law of SA states that a person holding dual citizenship has to use their South African passport to enter and leave the country. South Africans need visas to travel making the South African passport completely useless. Much easier for her to stick to her new nationality.
I find your post ignorant in regards to nationality, as Charlene is a native of South Africa, born & raised. Her great-grandfather emigrated there from Germany long before she was born.
Do some reseach and you shall see that this is true, and that she has every right to call herself a South African:
nationality - Dictionary definition and pronunciation - Yahoo! Education
Translation result for http://de.wikipedia.org/wiki/Charlene_Wittstock
Now regards "ethnicity", that's another matter all together, as South Africa is made up of 11 different official languages, and is ethnically diverse, with the first Europeans arriving in 1487: South Africa - Wikipedia, the free encyclopedia
As for the other stuff, lol, there are poor, rich, middle-class in 99% of the countries out there, that's a fact of life, South Africa is not unique in this regard.