She was born in Taal, Batangas on June 24, 1860 to Francisco Mariño and Eugenia Coronel. They were rich, religious and strict disciplinarians. She was educated in Sta. Catalina College and was married to Don Felipe Agoncillo, also of Taal, Batangas.

In Hongkong, she was requested by Gen. Emilio Aguinaldo to make a Filipino flag. She was assisted in this task by her eldest daughter, Lorenza and Mrs. Delfina Herbosa de Natividad, Rizal’s niece.

Mrs. Agoncillo made thie following written statement.” In the house at 535 Morison Hill, where I lived with my family, exiled from our country on account of the national cause, I had the good fortune to make the first Philippine flag under the direction of an illustious leader Gen. Emilio Aguinaldo y Famy…It took me five days to make that National Flag, and when completed, I myself delivered it to Gen. Emilio Aguinaldo before boarding the transport McCulloch…Gen. Aguinaldo is the best witness who can give the information whether or not that flag was the first to be displayed in Cavite at the beginning of the revolutionary government against the government of Spain in these islands.”

The Agoncillo family remained in Hongkong until 1906 taking care not only of their home but also of Filipino leaders who sought asylum in the island. At the establishment of the American regime, the family ended their exile and settled in Malate, Manila until their house was burned during the Japanese occupation.

She died on May 30, 1946, after the liberation of Manila.