Should one remain silent about the husband's mother who speaks ill of her and wishes her son would marry another, knowing that the fault in conception lies with her son? Or should she inform the husband about this, fearing problems?

We advise you to be patient with your husband's mother as much as you can, for Allah is with the patient. You can advise her kindly and warn her against harming a Muslim. Do not tell your husband if that will lead to his disobedience towards her. Instead, seek help from others who can advise her. Patience is the best remedy.