I can't imagine that the purpose of this prosecution was for any other reason than to make it possible for social services to control every aspect of these kids lives until they are 18, possibly longer (like until the baby is 18).
After all, the 13 year old mother is now a convicted sex offender and she will do everything they tell her to or her baby gets taken away.
In 5 years she is going to hate social services with a serious powerful passion. She won't be the first to give up their child to free themselves of big brother scrutiny and intervention.
She should give up her child to give both of them a better life. Adoption is a wonderful thing. Just because she can get pregnant does not a mother make.