You shouldn't keep people from their friends.
Mary is worried about her daughters friendship with a wild girl in their neighborhood.
Mary doesn't want her daughter to follow her friend into trouble.
Mary reminds her daughter of the values she has been raised with and trusts her to make the right choices.
Mary turns the girl away whenever she comes to she her daughter.
Mary's daughter gains confidence from being given responsibility to make her own decisions.
Mary's daughter grows resentful of her mothers highhanded approach.