Adolescents like that aren't girly; they are regular tomboys who climb trees, snitch apples, etc.
Notes. 1. I agree about tomboy. Dress isn't essential. Here's the OED definition: "A girl or young woman who acts or dresses in what is considered to be a boyish way, esp. one who likes rough or energetic activities conventionally more associated with boys." Even more on point, the OED quotes Margaret Mead from 1949: "To be a tomboy meant to run wild, climb trees, steal apples from orchards, fight, play boys' games."
2. I think that an academic in the 1930s would more like have written "adolescents" than my alternative, "teenagers." You can't say "girls" if you are following it up with "girly" (already used in the 18th century); if you have a different follow-up, of course you could.
3. Snitch (klauen) is more colorful than stehlen, of course. You certainly could use "steal."