How the bleep should I know?
Finn can do the spell to make the dead ones go away. But he'll be too late to save Ame; the boys will have killed her.
Finn could then find Ame's body and find Shadow's amulet still around her neck, maybe then he can bring Shadow back.
Aery's going to freak out when she realizes that Ame and Silly are dead. And Rowan. Oh, gods. But then she might be able to go back to her assassin's training, though she'll be nearly as weak as when she started, when she was seven. As long as Celaena doesn't beat her to teach her lessons, because then, holy flashbacks. But... We can make this work.