Do you think Jane in Twlight should look so young?

The whole Jane being a kid struck me. I always pictured her as an adult/young adult. The way she is described is "child like" never stating she is a child. I just feel that if you were describing a kid you would not say they were "child like" simply state they were children. How do you feel? Jane is best suited as LOOKING older, since in fairness she actually is. And by that I mean she's lived for AGES.