In 1913 Quintanilha was granted authorization to practice Law, five years before a Decree was issued permitting women to do this. In the same year she made her debut in court in the Portuguese capital of Lisbon as the country's first female lawyer. This was favourably covered by several newspapers, such as Diário de Notícias, O Século and República [pt]. She also worked as a public notary and as a conservator (record keeper) of the Portuguese Land Registry. She was also the first woman to have these responsibilities. In 1917, she served as president of the General Assembly of the feminist-inspired Portuguese Women's Crusade, an organization set up to provide support to conscripts during World War I.[3][4]
Quintanilha married Vicente de Vasconcelos, a judge, and they had two sons. She later moved to Brazil, where she collaborated in the reform of Brazilian law. She established an office in Rio de Janeiro and, later, one in New York. On her return to Portugal she worked as a lawyer for several French companies. Quintanilha died in Lisbon, on the 25 March 1967.[3][4]