Is it considered a sin for the husband's mother not to repay the amount she borrowed from him to purchase a clinic for his brother, despite the husband's need for the money for his children's education and expenses, and does this necessitate the wife feeling anger and a lack of inner peace towards them?

It is not possible to definitively state that the wife's mother is sinful. However, the son is permitted to demand his parents repay their debt according to the majority of jurists, and this is not considered an act of disobedience (uquq). Nevertheless, patience and seeking reward from Allah (ihtisab) are preferable and a commendable act of piety. Parents are allowed to take from their child's wealth under two conditions: that it does not cause hardship or harm to the child, and that they do not take it to give to another child. The wife has no right to object to her husband as long as he provides for her and their children; rather, she should comfort him and remind him of the reward (from Allah). She should also frequently seek refuge in Allah from worry, sorrow, inner whispers (waswas), and the scattering of affairs.