Is it considered a sin to turn away from a mother's conversation if it involves speaking ill of others, especially the father, due to its negative psychological impact?

An mother reminding her children of their father's flaws for the purpose of seeking advice or help in changing an evil is permissible, and she is not to be blamed. However, if it is without a valid reason, it is backbiting (gheeba), which is forbidden, and she must be gently and respectfully discouraged from it. You must be dutiful and kind to your mother, and her anger towards you without just cause will not harm you.