The woman is starting to get paranoid, but I can see why. A lot is at stake and she has both risked and given a lot to their cause. It might not be that Soo-ah did anything on purpose. It's what she does unknowingly or unintentionally that's dangerous. Like letting that stranger know of Gorae Byul. He might be harmless, but one day she might just meet someone or do something that isn't.