After she told him that she watched Yu Mei being assassinated without doing anything because she wanted her to die, she did notice the shift in his expression.
Maybe he was now taking some time to digest it or he was disappointed in her, she did not know what it was.
But Mia did not blame Han Jian Yu for it. Whenever she thought about that day, she felt disappointed by her own actions.
Living inside a box as a fox spirit for so long, she forgot that she was a human too. It was as if she had shed off her humanity at that moment when she watched Yu Mei dealing with all those men bare handed, and later after she was shot and pinned to the ground while those men tried to touch her inappropriately, she still continued watching the scene idly, waiting for her to die. Now that she thought back to that day, she felt like she sinned.
