She's 6. I like the character a lot. Was the first time I ever saw a child character in a video game other than pokemon. She's a pretty good white mage as well.
Relm in Final Fantasy VI or the Onion Knights in Final Fantasy III, but they really are no characters so - Relm. Or Vivi. And Palom, Porom and Rydia of course. And now Hope in Final Fantasy XIII.