Not a blonde.
Her blonde hair is simply just a thing hollywood did to her. They decided she was going to be a blonde. She is naturally a brunette. There actually exist picture of her without her blonde hair, and also, if you look at her eyebrows, they're very telling as to what her natural hair is. She even said in an interview "the powers that be" as she put it, wants her to keep her hair blonde.
Evil must be punished!