Can’t get pregnant

" We won't ask you why you killed those maids, once we are done dealing with this matter, we assure you that the Chu family will be answering us soon, but what we want to know is why did you have to do something this stupid?" 

When Empress dowager found out that the daughter from the Chu family tried to scheme against the daughter of their family, she was of course furious. But when she found out that Liu Hui Ying has actually let the maid confess that she has poisoned Ji Yu's womb and even told it to the Emperor, she was enraged. 

How can someone from the Liu family be this foolish? How can they be this big of an idiot to let such a golden opportunity pass by their hands?