How should a brother act towards his sister who has committed the abomination of adultery: should he let her continue her abomination, or should he disown her and expel her from the home?

The sister must repent to Allah the Almighty from adultery, by abandoning the sin, regretting it, and resolving not to return to it.

The brother should use the optimal approach to reform her, whether by boycotting her if that will lead to her rectitude, or by drawing closer to her and treating her kindly, in addition to using various da'wah methods such as visual and audio materials, booklets, and kind words, while persistently supplicating for her.