What should a daughter do who fears divorce between her parents, as her mother commits indecency and her father and sister have not spoken to her for four years?

The mother's act of fornication is one of the most heinous major sins, and severe warnings for its perpetrator have been mentioned in the Quran and Sunnah, such as Allah's saying: "And do not approach unlawful sexual intercourse. Indeed, it is ever an immorality and is evil as a way." (Quran 17:32) The prescribed punishment for a married female fornicator is stoning. The questioner must advise his mother and remind her of Allah's punishment and the heinousness of her act, and that if she repents, Allah will accept her repentance. He should also conceal her sin and treat her kindly in matters that do not lead to disobedience, and repent from severing ties with her. If she insists on fornication, it is better for the father to divorce her for fear of her corrupting the children.