In all the fictional stories i read i've never seen a more diabolical and malignant character than this bitch. She purposely said these things about Sei and Yuiko in front of the others in order that he would be laughed at and bullied even more later. She knows that the more Sei becomes withdrawn from society the more he remains dependent on her, she doesn't want her son to grow up and be independent, she wants him to stay her innocent plaything.