In the studies about Medieval Spain, only men were believed to be susceptible to amorous passion or lovesickness. I propose that a more nuanced and complete understanding of women’s roles and actual behavior can be reached by analyzing the same medical and philosophical treatises that deny them the possibility of suffering from lovesickness. In fact, my readings of texts such as Grisel y Mirabella (ca. 1475), Celestina (1499) and Tristán de Leonís (1501), demonstrate that women’s behavior in literary representations is guided by the same symptoms experienced by lovesick men, symptoms that women sometimes suffer even more intensely than men. The topic of women’s lovesickness and the rhetorical devices used to depict the power and influence of women in medieval Spanish literature has not been formally studied due to the misjudgment that this malady was an exclusively male condition. This study shows that women's roles in Juan de Flores' sentimental romance Grisel y Mirabella (1495) were influenced by lovesickness or amor hereos. I also discuss how linguistic and narrative theories, as well as historical rhetoric about sexuality from the time of this text, helps us to understand how lovesickness influenced the female discourse created by Juan de Flores in the late Middle Ages. In doing so, I argue that the female characters were an alterity of power to their real counterparts in society. In some narratives they are resistant within the text, in others they struggle to act upon their desire without fearing the moral and social consequences.