What is the religiously mandated action required from the wife towards her husband's sister who accused her of infidelity, backbiting, and stealing from her brother, after the wife had cared for her during her illness despite her repeated insults?

It is advisable to be patient, to make abundant supplications (du'a), and to remember Allah (dhikr). One should offer advice to the sister gently. If she causes harm and does not benefit from the advice, it is permissible to shun her if there is a benefit in doing so. If there is no such benefit, then the benefit lies in patience and maintaining ties, and repelling evil with good. It is the wife's right that her husband provide her with an independent dwelling. She is not obliged to live with his relatives, and the dwelling may be rented.