During the Philippine–American War, Magbanua participated in several battles against American forces, as did her brothers. Her brothers were both ranking officers—Pascual was a general while Elias was a major. On 11 February 1899, Magbanua fought in the Second Battle of Iloilo City. Along with General Martin Delgado, Magbanua defended Iloilo City against the advancing forces of Brigadier General Marcus Miller. This battle ended in defeat for Magbanua and Delgado, as American forces took Iloilo without a single reported casualty. On 10 March 1899, Magbanua participated in the Battle of Balantang, Jaro, along with her brother Pascual. This battle resulted in Philippine forces retaking Jaro from the Americans. For her valor, Magbanua was given a prominent place in the celebration that followed, and led her troops into the city while riding a white horse. Also in 1899, Magbanua participated in the defense of the Balantang-Tacas-Jiabo-an line.
