naive — having or showing unaffected simplicity of nature or absence of artificiality; unsophisticated; ingenuous.
girlish — of, like, or befitting a girl or girlhood: girlish laughter.
hoydenish — a boisterous, bold, and carefree girl; a tomboy.
adjective teenage
juvenile — of, pertaining to, characteristic of, or suitable or intended for young persons: juvenile books.
adolescent — Adolescent is used to describe young people who are no longer children but who have not yet become adults. It also refers to their behaviour.
