Or maybe the right thing to do is to try to help Sammy see the evil she is committing. That could involve a Socratic approach that will help uncover the underpinnings of her position. If that fails and Sammy either obstinately refuses to see or for some reason cannot see, then it makes sense to part ways. You gave it a shot, you tried being charitable, but you ultimately cannot force another to accept the truth, nor should you want to. Everyone is morally responsible for his or her own views at the end of the day.