Easier said than done, they usually have your 'balls' in a not so nice place.
It must be tough working as a civil servant, the option is usually to join in the eating or you quit, like some cult of some sort, quitting is usually not an option by the time you realize what is happening you already have blood on your hands the blackmail is real and if you refuse to eat we read in the news how you were shot dead at a gas station and your iPhone 6 plus was not taken.
In the meantime, Magufuli is firing the heads even when what he finds wrong is not their direct responsibility, like patients sleeping on the floor of a hospital, the CS for Health would be long gone with the many cases of negligence happening around.
How about the company whose directors happen to have won several tenders in the said ministry and her son happens to be driving the Aston Martin belonging to one of the directors?
We all know what happens and how it happens.
Until we hire a Magufuli as president, someone whose name is clean and doesn't have someone somewhere holding their balls and therefore influencing what they do or do not do, the cycle continues.
In the meantime, asking him to fire her is the same scenario when your son is deeply in love with a woman that the rest of the family does not approve of. If I were him na hatuna shida ya pesa, I would ask her to step aside.