Is boycotting a mother who secretly married and caused reputation problems considered disobedience and a sin, especially since she does not listen to advice?

Allah has commanded righteousness towards parents and benevolence towards them. The mother's right is great, even if she is a disbeliever. The questioner should advise her mother gently, kindly, and respectfully, without raising her voice, especially if the marriage is legitimate and fulfills the conditions and pillars.