You point out that you're pretty sure you killed one of the knights, but leave to yourself that you still believe her powers to be utterly insane. Sighing, you tell EMily that you cannot think of anything that justifies killing an unarmed prisoner. Besides, you don't follow your head, but your gut. You can tell Sophia is not a mass murderer and you can tell that Seras is not anxious over what she has done, but rather how others have reacted to it. The reason you left in the first place is that you know others would have been quicker to forgive her than you, and you did not come back to kill her either. That, you conclude, is the best she'll get from you.