I wasn't sure which was correct so I looked it up in the dictionary and teenage is correct. My spell checker agreed. However, no one says juveniles except for the police.
It accepts "youthful girls" but since all girls are youthful it's not great english. I have learnt to type such rubbish English in DL because the risk of losing a heart by typing good English is too great
"Young girls" would be more acceptable English here