Born in the city of Poços de Caldas, in the state of Minas Gerais, in 1904, Mello worked as a domestic and became the first union leader of this occupation in Brazil. Outraged with extent of prejudiced advertisements throughout Brazil and the rampant discrimination against women in the job market, she founded various organizations to fight this discrimination in the cities of Santos, Campinas and São Paulo, all of which are cities within the state of São Paulo. In 1936, she founded the first association of domestic workers in the city of Santos, São Paulo.
Throughout Brazil in her time (and even recently), it was common to see want ads in newspapers that requested domestic workers that “prefere-se branca” or “we prefer white women”. After having consistently read racist ads in the newspapers, she confronted writers at the Correio Popular newspaper and inquired as to why such racist wording was used. The newspaper soon prohibited such advertisements of such a racist nature. As black girls were prohibited from joining dancing schools, she organized the first debutant ball (in Campinas, São Paulo) for black girls with the objective of raising their self-esteem.
A militant of the Movimento Negro (Afro-Brazilian civil rights organizations), Mello built a reputation for confronting the rich and powerful in defense of the poor, black people and women. Domestic workers are often treated horribly in Brazilian homes, sometimes targets of sexual abuse and often are not able to attain an education. Under her leadership in 1988, three years before she died, Mello helped transform the Domestic Workers Association of Campinas into a official union.