The Peanuts girl known for having naturally curly hair is Frieda.
Frieda’s defining feature is her red, naturally curly hair, which she proudly mentions so often that it becomes one of her recurring jokes. She is particularly protective of it because hats and similar headwear might hide the curls. In one baseball storyline, she is the only girl on Charlie Brown’s team who refuses to wear a cap for that reason.
Charles M. Schulz introduced Frieda in 1961. The character was inspired by Frieda Rich, an artist Schulz knew from his years at the Art Instruction Schools in Minneapolis. Early strips portray Frieda as a chatterbox who sits behind Linus in class and talks so much that he claims he cannot hear the teacher.
Frieda was a regular character during the 1960s, but she appeared less often as newer members of the Peanuts cast became more prominent. She remained recognizable in later animated appearances and returned in modern adaptations, including The Peanuts Movie, where her full name is given as Frieda Rich.