She was now starting an open war

Zhao Ming wanted to discipline the servants and punishing Hao Mei was the first step towards it. If she didn't punish anyone, they will think that she was joking and will not take her seriously. 

She has to show them who is the boss. Otherwise, they will always treat her like a nobody and Xiao Li will take all the respect and benefits.

She does not want to be a kind-hearted protagonist who will be pitied by everyone. She prefers to be the villain and prefers to return them what they have sown.

She is not kind. She is cruel and ruthless. And they have to deal with her until she is in this world. 

Though Wen Xu looks like her late mother but there is not a single trait of her mother. That's why she doesn't care about her either.

If she treated her like her mother, then it will be insulting to her real mother who is in heaven. 

Wen Xu does not deserve to be called by Mother by anyone. She feels pity for Ji Cheng sometimes.