Sora said there were different worlds, as many as there are stars in the sky. Maybe you're from a different world from ours, but within the same kind of... universe? And given we both know about the keyblade, we must have some sort of uniting factor eventually, since I can't imagine magical swords are very easy to come by. Maybe we just haven't had the right trigger to remember it properly yet!

[She grins.]

Pfftt. I'll show you lousy. One of these days, I'm gonna be such a legit princess you won't even know what to do with yourself! So there.