But if she is a heartless without a heart, how can she weild a keyblade?
I seem to remember a strong heart is requirment for keyblade wielding.
Well except for Roxas seeing how he is/was a nobady, but then again he could of possibly had some sort of heart, because of his emotions, which nobodys are supposed to lack, but he is a special nobody so that might could explain his emotions too, or maybe it was because he was alive as the same time as his heart(sora) and thats why he feels them, or something to do with ven. But now im off topic.