Firstly, if you read the article, the 16-year-old said she WAS forced to do things she didn't want to do, so I don't know why you would say "No one forced this young woman to do what she did. She made a choice."
Secondly, maturation is a process; it's not as though one day, in the life of each child, a switch is thrown and, voila, instant maturity! That's one reason why legal rights (driving, voting, drinking, full emancipation, etc.) are granted on a gradual basis.
Thirdly, equating "sexual transgressions" with "brutal murder" is like comparing apples and oranges.