and I love Pocahontas for it :)

jasmine? really?

Pocahontas was the first that came to my mind.

princesslullaby: jasmine was quite radical. she wanted to marry for love, nothing else even though it was expected of her to marry a prince. but i wouldn't say she's the most radical. mulan, pocahontas and ariel the most.

I would say Pocahontas or Mulan. Both changed the way their people viewed certain groups. Pocahontas helped her tribe see that the white settlers were human as well (and vice versa). Mulan made all of China realize the value of women.

and pocahontas

Pocahontas immediately came to mind, but when I took a minute to think, Mulan was the predominant princess.
Pocahontas was radical about just one main point - race. Mulan pretty much overturned every single aspect of gender, much more so than Poca. She challenged the image of women, the way women should act, what women could do and the role of women in relationships.