Ji Wu Jiu regretted saying those words towards Ye Zhen Zhen. She has already suspected him from the start, and for him to purposely say those words, he is afraid that she will only suspect him more.
All in all, it was becasuse she has never believed him in the first place. Most probably ever since she entered the palace, she has always been wary of him, afraid that he will harm her, or harm her maternal family. This time, he was only afraid that she will think too much.
Ji Wu Jiu was getting reckless. It was not that he has never thought of bringing Ye Family down, even he wants to, it will never be using this type of method. No matter what, Ye Xiu Ming was once his teacher, he would not be such so cold hearted to give the name of treason towards Ye Xiu Ming.