But this quiet enjoyment of peace and love was not long allowed to the beautiful ruler of Portugal. Her half-sister Urraca, the Queen of Castile, Leon, and Gallicia, had been hitherto too much engaged in fighting with her second husband, Alfonso I. of Aragon, to pay any attention to her; but she too was a warrior princess, and in 1121 she ordered Theresa to surrender the city of Tuy. Theresa refused, and Urraca led an army against her, which defeated the Portuguese at Tuy, and eventually the queen took the Countess of Portugal prisoner after a long siege of the castle of Lanhoso. It seemed as if the nascent independence of Portugal was about to be crushed, but Bishop Gelmires came to the assistance of Theresa, who had done so much for his friends and relatives, the De Travas, and threatened to attack Urraca unless she made peace with her half-sister. Urraca was forced to comply, and the treaty of peace which was then signed marks another stage in the growth of the independence of Portugal, for in it Donna Theresa is styled Infanta, and treated as the equal of Queen Urraca, who further promised to cede to her the cities and districts of Toro, Zamora, and Salamanca. For the next few years the careers of the half-sisters were singularly similar. Queen Urraca showered favours on her lover, Don Pedro de Lara, until her young son, Alfonso Raimundes, assisted by Bishop Gelmires, revolted against her; while Donna Theresa, with equal blindness, devoted herself to her love for Don Fernando Peres de Trava, and thus aroused the hatred of her boy-son Affonso Henriques and of Paio Mendes, who in 1121 had succeeded Mauricio Burdino as Archbishop of Braga. Her quarrel with Paio Mendes commenced in the year after he became archbishop, and well illustrates the attitude of the Portuguese bishops. As long as Theresa had remained the living symbol of Portuguese unity and independence the bishops had followed her, but as soon as she showed her love for a Gallician nobleman they turned against her. Paio Mendes was quite ready to lead the malcontents, for he was the brother of Count Sueiro Mendes of Oporto, surnamed the Great, who was the head of the purely Portuguese, as opposed to the mixed Portuguese and Gallician, nobility. In 1122 Archbishop Paio protested against the gift of so many important posts to Don Fernando, and the proud countess immediately cast him into prison. She was obliged in a few days to release him, for fear of a papal interdict; but she had made a bitter enemy, who was soon to have an opportunity for revenge.