Rivera Lassén obtained a Juris Doctor from the University of Puerto Rico. As a jurist, she has writings, articles, essays, and even short stories and poetry, published in magazines, anthologies and newspapers both locally and internationally. Together with Dr. Elizabeth Crespo Kebler, Ana Irma published the book "Documents of Feminism in Puerto Rico: Facsimiles of History", which talks about the feminist movements of the seventies in our archipelago, and represents an invaluable contribution to the study of women's contributions to the history of Puerto Rico, the Caribbean and Latin America. 

She received the Capetillo-Roqué medal from the Senate of the Commonwealth of Puerto Rico, a special distinction for her work and exceptional contributions to achieve gender equity and improve the social conditions of Puerto Rican women and for her struggles in favor of human rights. Likewise, the Puerto Rico Bar Association recognized her struggles for civil rights and against racial discrimination with the Martin Luther King/Arturo Alfonso Schomburg Award. 

She was also awarded the Nilita Vientós Gastón medal for her struggles in favor of human rights, her work as a lawyer, her creative work, her work as a humanist and defender of the arts. She is recognized as an expert on human rights, gender and race by the Women's Division of the Economic Commission for Latin America and the Caribbean (ECLAC), an agency of the United Nations.  

She was co-founder of historic organizations such as in 1972, Mujer Intégrate Ahora, MIA, the first feminist organization of the so-called second wave of feminism in Puerto Rico; Comunidad de Orgullo Gay in 1974, first organization in defense of LGBTTIQ+ rights in Puerto Rico, in 1992, the Unión de Mujeres Puertorriqueñas Negras, which emerged after several efforts to organize around this issue in Puerto Rico and in turn be part of the regional founding of the Red de Mujeres Afrolatinoamericanas, Afrocaribeñas y de la Diáspora; she has also been part of the founding and development of other important entities and networks both in Puerto Rico and regionally. 

Since she was 16 years old, her participation in human rights activism, in all its diversity, has been constant and permanent. She was a commissioner in the Commission for the Improvement of Women's Rights when that entity was initiated and later when the Office of the Women's Advocate was created, she was also present and presided over its first Advisory Council.

From 2012 to 2014 she served as President of the Puerto Rico Bar Association, being the third woman to do so, the first Afro-descendant and the first person from the LGBTQIA+ community and also chaired the citizens' movement Vamos Puerto Rico from 2015 to 2019.  

Rivera Lassén recently received two major recognitions from the USA TODAY Network for her significant impact in her community and across the country. She was named USA TODAY's Woman of the Year in 2023, standing out for her work and contributions. In addition, in 2020, in commemoration of the centennial of the 19th Amendment, she was recognized as one of the Women of the Century, being one of 19 women from U.S. territories who have made notable contributions to their communities.

Currently, she is part of the Advisory Council of the Latin American and Caribbean Committee for the Defense of Women's Rights (CLADEM) and is part of the Advisory Council of the Afro-Latin American, Afro-Caribbean and Diaspora Women's Network. She was one of the spokespersons of the Puerto Rican Concertation against the Fiscal Control Board and was co-founder and president of the Movimiento Victoria Ciudadana and candidate for Senator for Accumulation. In November 2020 she was elected to the position. Today she is Senator for Accumulation, Spokesperson in the Senate of Puerto Rico for the Citizen Victory Movement, president of the Human Rights and Labor Affairs Committee of this body and general coordinator of the Citizen Victory Movement.