What is the ruling on refraining from speaking with the husband's mother, who refuses to believe her daughter's betrayal of her husband and blames the questioner for not standing by them, and what should the questioner do regarding this situation?

It is obligatory to conceal the wife's sister [i.e., her sister-in-law's sins] and not spread news of her disobedience, for the Prophet, peace and blessings be upon him, said: "Whoever conceals a Muslim, Allah will conceal him in this world and the Hereafter." If it is possible to advise her, then advising her is obligatory; otherwise, one should denounce it in their heart. The husband must restrain his sister from evil by all means. If he is unable, he should inform someone among her relatives who can restrain her. It is not permissible to abandon the husband's mother, and the better of the two is the one who initiates the greeting.