Her first tenure as regent lasted from 1420 until 1423, and her second from 1432 until her husband's death in 1458. As such, she was forced to handle the conflicts with the burghers and the peasants which broke out during her husband's reign. When Alfonso was captured after his defeat at Ponza in Italy in 1435, she organised the funds to pay his release. On one occasion, Queen Maria of Aragon and Queen Maria of Castile, the two cousins and sisters-in-law, mediated the peace treaty between Aragon and Castile in Valladolid on behalf of their husbands; it was said that there would have been peace in Spain at that time if the Queen of Castile had as much authority as the Queen of Aragon. In 1454, after her brother's death, the Queen of Aragon travelled to Castile to negotiate with its new King, her nephew, Henry IV. She stayed in Arévalo, Castile, until the year before her death in 1458.