Yeah, it is not going to be easy to make these stories kid-appropriate without flat-out lying. I'm not afraid of exposing my daughter to tales of warfare, but I'm going to be skipping over a lot of rape.
I bought her a couple of books to get started, one about Queen Elizabeth and one about Eleanor Roosevelt -- First Lady is the closest thing we've got to an American princess, right? Surprisingly, they didn't have one on Jackie O. But the more I think about it, the more it looks like Princess Grace of Monaco might be the best place to start. She died youngish and suddenly, but at least she wasn't beheaded or anything.
Additionally, I want to adapt the Shakespeare play from which we derived my daughter's name into a version she can understand. I think it's possible -- kids aren't real concerned with a villain's specific motivations; they can just accept that Don John is a Bad Guy without further explanation. I intend to use this to my advantage.
At the bookstore, Chaos Girl chose a pop-up book on human biology. It is pretty cool, and she seemed to grasp the general concept that in addition to the body parts she can see and name, we also have body parts inside, like a heart, lungs, and intestines. So that was neat.