What should a person do if their mother mistreats servants due to a past experience, refuses advice, and they perceive her silence as an endorsement of injustice?

If Allah grants a Muslim power over those under his authority, he should remember Allah's power over him. The Prophet, peace and blessings be upon him, was the best of people in character towards his servants. Among the rights and manners that a Muslim owes to those under his authority are: feeding them from what he eats, clothing them from what he wears, not burdening them with what they cannot bear, paying their wages in full, not insulting or striking them, treating them kindly, and overlooking their mistakes. Allah has warned those who oppress a laborer or anyone under their authority of punishment on the Day of Resurrection.