Why is it legal for Correction officers and Cops to teen girls in State Prison?

It isn't legal. Problem you are having in your story is that no one cares enough to attempt to substantiate your claims. It isn't a matter of legal or illegal, it is either disbelief in your accusations, or it is a level of social disregard for a traumatic event done in a facility specifically designed to house such crimes. You determine which is the case. Either way this exclamates the problems within our society.