If her father hears about the promise and agrees, then the young woman must do the thing she promised.
“A young woman might still be living in her father’s house. And that young woman might make a special promise to give something to the Lord.
But if her father hears about the promise and does not agree, then she is free from her promise. She does not have to do the thing she promised. Her father stopped her, so the Lord will forgive her.