Stargirl by Jerry Spinelli is a tween story about a boy's (Leo) impressions of a girl who was briefly at his school. She was as bohemian as they come and she sported a memorable name: Stargirl. She gives notes to everyone, serenades people with her ukulele, and talks to a cactus.
After all the positive effects she's had on the school, she's still emotionally broken down and forced to normalized. Her grand experiment supported by friends, family, and neighbors, comes to an abrupt stop and she sees the error of her ways. Thus she returns to her given name just before moving away to a different school.
I don't normally give such a straight up plot review, but the book is rather disheartening. It's boy's nostalgic account of a girl's ambitions being crushed by the demands to fit in. He feels bad not because she's been forced to surrender, but because she's no longer the cool, unique, girl friend.
A far better version of the same set up is a goofy Disney XD cartoon series, Star vs. the Forces of Evil. The same types of characters are there and she does similar, off the wall, things for her own entertainment and in the name of friendship.
Leo's equivalent is Marco. He's also Star's host, as here she's an extra dimensional exchange student. Though there's certainly chemistry between them it's strictly one of friendship. Star has her eyes on the synth playing emo kid and Marco has his on a skateboarding girl. That means their relationship and her character growth within the series don't hinge on how good of a girl friend she is.