She served as an OAS ambassador until 1960, when she was selected as one of the inaugural members of the Inter-American Commission on Human Rights (IACHR). Between 1960 and 1972, Acuña was Costa Rica's delegate on the IACHR and traveled throughout the member countries investigating economic, social, and political conditions which impacted human rights. She examined various types of cases, including the 1961 pro-Castro demonstrations against President Joaquín Balaguer; allegations made in 1963 that Cuba had laid a mine field around Presidio Modelo on the Isla de la Juventud to prevent the liberation of political prisoners housed there; and deaths resulting from 100 Hour War between El Salvador and Honduras in 1969. After retiring from the IACHR, Acuña remained active and continued attending Inter-American Commission of Women meetings. She also began writing her autobiography, but by the end of the decade was unable to continue as her health declined. On 28 September 1982, she was awarded Costa Rica's "Benemérita de la Patria" (an award for meritorious service to the motherland). Acuña died on 10 October 1983 in San José, Costa Rica and was buried at the Cementerio Monte Sacro in Curridabat. She is remembered in Costa Rica for her dedication to the fight for women's rights and contributions to human rights. She is recognized as a pioneer who laid the groundwork for the Juvenile Court System, which was formally adopted in 1956, and for laying the foundation for women's citizenship and policies to create a more egalitarian society in Costa Rica. Since 1984, the National Journalism Prize, given to authors who promote the ideals of women's equality in Costa Rica, bears her name and is awarded by the National Institute of Women.