I think I went overboard with my shapes unfortunately, but I'm going to go back and refine.
The initial shape is a circle since it's youthful and feminine. The 2nd shape I used is a rounded rectangle, as it adds definition without being pointy and evil-like.
Here are the shapes combined along with the traits I kept in mind.
She's an Elizabethan hipster. Yep. An original.
Her face looks sort of old for someone who's supposed to be like 13 years old, but I have a few ideas to make her look younger, and will upload a refined sketch soon.