Numbers 30:3-5 (DBY) 3 If a woman also vow a vow to Jehovah, and bind herself by a bond, in her father's house in her youth, 4 and her father hear her vow, and her bond wherewith she hath bound her soul, and her father shall be silent at her, then all her vows shall stand, and every bond wherewith she hath bound her soul shall stand. 5 But if her father prohibited her in the day that he heard, none of her vows, or of her bonds wherewith she hath bound her soul, shall stand; and Jehovah shall pardon her, because her father prohibited her.
Is that purposeful enough for you?
I don’t believe that “in her youth” would limit his authority to her first menses as long as she is still in her father’s house.