What is the ruling on the wife's mother asking her daughter's husband to have sexual relations with her, and how should a conservative Muslim family deal with this situation, taking into account the mother's special circumstances and her desire to reclaim her inheritance?

The prohibition of zina (unlawful sexual intercourse) is an indispensable principle of Islamic law. Enabling a woman to commit fahisha (an abominable act) with her daughter's husband is forbidden and reprehensible. The daughter's husband must be cautious of this woman and it is not permissible for him to be in seclusion with her, lest Satan lead him into fahisha. Allah Almighty says: "O you who have believed, do not follow the footsteps of Satan." The woman's claim of loving her daughter's husband as her own son is inconsistent with her request for fahisha. Her open admission of this to her daughter indicates her loss of religious commitment and shame, for "If you feel no shame, then do as you wish." It is impermissible to pursue unlawful means to claim rights, as the end does not justify the means in Islam.