With the choice comes the responsibility, ya know. 
Both statements appear over the top. The girl made a terrible mistake and the boyfriend is a lowlife who took advantage of an underaged girl.
The boy should be prosecuted to the fullest extent of the law. However the girl needs to understand what she did is wrong. Having said that the girl should not be made to feel she has ruined her life and is doomed to eternal damnation. She is only fifteen years old and I am sure God will find a way to forgive her.
Hopefully the girl comes from a good family and realizes what she did is wrong. Let's remember that all of us sin. Good people sometimes do very stupid and bad things. I am assuming she feels terrible about what she did. She is probably crippled with shame, regret, saddness and fear.
Of course she should be appropriately punished and sanctioned for her actions by her parents. However, what she probably needs now is love, guidance and forgiveness. Her father will not be able to give her any of those things if he is in jail.
Your children are blessed.
With the choice comes the responsibility, ya know.