I don't think it has anything to do with the color of her skin, or her being shy. When I first heard of her a couple of years ago, I found out that both her and her husband chose to live in New York so that she could continue to work and they both could live a low key life, out of the public eye.
They both participate in things with the RF. And thier son is well acquainted with his cousins, aunts, uncles, and grand parents.
I think they just choose to live their life out of the public eye and as normal as possible.
And from what I've read, the entire family is this way. It's just that they live in the U.S. and the rest of the family live in another country!