Is a mother sinful for scolding her elder daughter and punishing her by suppressing her and preventing her from speaking, and belittling her in front of her younger sister, due to the suffering she experienced during her pregnancy and childbirth with her?

There must be equality among children in apparent matters, based on the hadith (definition) of Nu'man ibn Bashir: "Be just among your children in giving as you would love them to be just among you in dutifulness and kindness." The mother has acted towards this girl in a way that violates Islamic law, punishing her for something over which she has no control. Therefore, she must fear Allah and treat her like her other children, and not punish her for something Allah has decreed. This behavior has serious consequences for the girl physically and mentally, and it may lead to her disobedience and hatred for her children.