My fist run I sais the same, but in this run I said:
- Hells! Can you read my thoughts?
- I'm nos doing a thing you say! This isn't who I am.
- I won't let myself touch another innocent.
- Stop talking as if you're brewing me a cup of tea! We're talking about real people!
I think they are the most negative responses to killing Isobel. And yet, after talking to Isobel and telling her that I'm not going to kill her, the game follows me without marking the mission and without the second visit from Sceleritas appearing.