[Is stiff with anxiety as they walk, but it eases a bit with his words. He doesn't sound angry? So maybe it's not as bad as she thought it might be.]
It--It was my own fault. I'm sorry. I should have known better. [She's not exactly sure what she's apologizing for. The things she told him, or for not having realized sooner who she was telling them to...or for the situation in which the truth was revealed.]