She is a modern Venus, in a way that her beauty as an ideal has spreaded all over the western hemisphere. That is why an artist like Mark Quinn use her as a muse. We may like it or not, but that is a fact. Also, I'm not talking talking about her as a person, but as a symbol. Most people that see a picture of her don't really know if she snorts cocaine or not. We also don't know anything from the model that posed as Venus (de Milo), yet she also represents the ideal of beauty of a certain moment in history.
The thing is, I don't believe that Kate is beautiful at all; what she is is expressive of a 'type' and she has had the ability to move with that type over a time-frame that's amazing. Of course, she's also partly responsible for forming that type and the changes within it, which makes it somewhat more simple for her.