The sisters believe that they will never see Mirabella again because she is expelled from St. Lucy's Home for Girls Raised by Wolves, bemoaning their unwillingness to return to the wild woods with her.
Expulsion of Mirabella shows that she cannot return to the St. Lucy's Home for Girls Raised by Wolves. She is forced to return to the wild wood since she cannot be reformed to become human-like.
Mirabella, as a wolf-girl, fails to adapt to human cultural behaviors and expectations. Mirabella does not belong to the human class, having failed all efforts aimed at civilizing her culture.
For example, Mirabella strangles some ducks since killing animals agrees with her second nature as a wolf.
Thus, the sisters' belief that they will never see Mirabella again stems from her expulsion from the St. Lucy's Home for Girls Raised by Wolves.
The answer should be A. We know Dev is being playful when he breaks a smile, which is said in the stage directions. It also says he thumbs his axe mischievously, which means he is being playful. Hope this helps!
