"I just can't stand Tong Sanlang, so I schemed against him. Besides, this is also what Tong Sanlang's parents asked for. Your Majesty, if you really want to punish someone, Tong Sanlang's parents can't escape the blame either."
Bai Zhi didn't betray Yao Xian, and took all the responsibility upon herself.
Moreover, the matter was mainly orchestrated by her; Yao Xian merely gave some advice at a crucial point. She didn't have any evidence to prove Yao Xian's involvement with the matter.
Emperor Yong'an saw that although she bowed her head, her face still wore an unconvinced expression. He sighed lightly, "Filial piety has its place. As long as Tong Sanlang's parents didn't kill him, their issues are domestic matters, and I have no place to intervene."