Movies are adaptations -- it's not possible to translate every bit of a literary work into a visual equivalent. When liberties are taken, the results can be fantastic: see Where The Wild Things Are for a supreme example of this (in my opinion). Or changes can be nearly irrelevant, as in LOTR's giant spider battle moving from part two to part three.

I haven't read these books (though I do love me some YA fiction) but unless the protagonist's racial identity is a central component of the plot, this doesn't sound like whitewashing. I'm more concerned about the potential for pro-ana type bullshit.