My understanding is, if you register a car, get a license, rent a home in your name, get power or internet connections in your name, or do any business in California, they tax your income. Or, at least you will have the opportunity to prove to the state of California that you are not a resident. She is probably living in California without paying California income taxes. (That would be quite a feat.)
She says she earns income but her mommy supports her.