This hasn't been mentioned, and I'm jumping forward a bit, but Brienne makes Catelyn swear that she will not get in the way when she wants to kill Stannis. I can't recall if such a conversation exists in the books, or if they even come to the conclusion that it was Stannis, but could this possibly lead to Brienne's word which saves her from her hanging at Stoneheart's command in the future of the show? Maybe not as a reason to get out, but to tell Catelyn basically that she never got that opportunity and she was denying it to her. Just throwing it out there. :)