Is hurting a colleague and treating her badly after you have assumed the position of manager and docked part of her salary considered an allegiance to injustice, especially with the feeling of pressure from rejecting colleagues' demands and the fear of affecting business interests?

This action is clear injustice. One who demands their right should not be mistreated or punished, nor should a portion of their salary be deducted. Neither the pressure from colleagues nor the fear of affecting business interests justifies usurping people's rights. It is not permissible to avert injustice from oneself by perpetrating injustice against others. Ibn Taymiyyah said: "He did not repel injustice from himself except by oppressing his partners, and this is not permissible." Ibn Hazm said: "The text never permitted him to repel injustice from himself by oppressing others who had not transgressed against him."