How can a Muslim woman, harmed by the continuous abuse of her husband's brother's wife, protect herself from her evil and deal with her provocative actions, which include false accusations, defamation, and forming alliances against her?

Harming a Muslim is forbidden. The Prophet, peace and blessings be upon him, forbade it and condemned its perpetrator. The Quran describes harming believers without cause as a clear calumny and a manifest sin. It is incumbent upon anyone who harms others to fear Allah and cease their harmful actions.

As for the one who is subjected to harm, they should be patient and not reciprocate evil with evil. Rather, they should respond with goodness, seeking the pleasure of Allah and the contentment of their spouse. They should open the door to communication with kind words, cheerfulness, reciprocal visits, and gift-giving, for these things open hearts and remove resentments. If this does not prove beneficial, then they should exercise patience, refrain from harming in return, stay in their home, and strive in the worship of their Lord. Their harm will not afflict them.