Around here, Anne Frank and several other books(indluding "Number the Stars")about the Holocost are read in 4th grade, with quite a bit of discussion. It seems a bit young to me, but that being said, my generally sensitive son was fine with it (emotionally) and learned a lot. I think they try to place the emphasis on how discrimination is bad, about brave things people do to help others, and how we need to learn from history.
I, too, am definitely going to reread it with an eye toward her giftedness. As soon as I read your post MsFriz, I immediately knew you were right!
