I know I can't convince you because you see the fetuses life as trumping everything. However I think these girls and women have a right not to go through with a pregnancy they have no responsibility in creating. I think it would be heroic to do so but not a moral obligation. I think I have a right not to have my body used for other people's purposes including bring a child into the world. And for minors who can't understand most of this I think their bodies should not be used by adults to secure our values.
A for your scenario I think you would have to tweak to address adult women and minors. for adults the other person is inadvertently doing the torturing and their survival depends on my survival. I think at that point it becomes murky, which is my point.
Or it like asking, would you torque a child to save someone's life. I think then the responsibility for the loss of life falls on the rapist and not on the child or the adults helping her.