How can one deal with feelings of hatred toward a husband who married a second wife and whose treatment has changed?

A wife's feelings of resentment towards her husband might stem from his marriage to another woman or his ill-treatment of her. If it is due to his marriage to another, this is not a sin as long as he maintains justice among his wives. Allah has permitted a man to marry up to four women if he is able to deal justly with them in terms of sustenance, clothing, and lodging. However, if the reason is his inclination towards the new wife, then he is sinful and must act justly. Polygyny has great wisdoms, including increasing the Muslim nation, the fact that men are fewer in number and more susceptible to death than women, and that fewer men are ready for marriage compared to women. If a man fears he cannot be just among them, he should restrict himself to one wife. A woman should examine herself to find the reason for her husband's change; if she finds any shortcomings or defects, she should rectify herself. If the shortcoming is on the husband's part, she should be patient with him and know that her staying in her home is better for her than destroying it, and that victory comes with patience, relief with distress, and ease with hardship.