Answer
Marie de Médici, the Queen Mother, was Richelieu's bitter rival. Their conflict stemmed from their opposing political views and ambitions. Médici, a devout Catholic, favored a pro-Habsburg foreign policy, while Richelieu, a pragmatist, sought to strengthen France's power and reduce the influence of the nobility. Richelieu's rise to power and his efforts to limit Médici's authority led to a bitter rivalry between them.