What should a son do who secretly married a woman nine years his senior, whose mother is angry and insists on divorce because she knows the wife is ill-mannered, immodest, and too lenient in her interactions?

A man must obey his mother in divorcing his wife if she is immodestly adorned (mutabarrijah) or lenient in her interactions with non-mahram men, because this is considered an enjoinment of good. Furthermore, he is responsible for preventing her from these evil deeds, and if he is unable to do so, then divorcing her becomes recommended or obligatory.