[6][7] Her father is now-retired Regional Trial Court judge Sixto Roxas Guanzon, while her mother, Elvira Causing Villena, is a lawyer and former Cadiz vice-mayor.

[9] Guanzon also holds a master's degree in public administration from Harvard University's Kennedy School of Government,[10] where she was an Edward S. Mason fellow and class marshal.

[4] She was appointed after several other candidates had declined to be mayor of Cadiz, fearing violence from local strongman Armando Gustilo,[11] who had played a key role in the Escalante massacre just a few months earlier, in September 1985.

Gracia M. Pulido Tan and Commissioner Heidi L. Mendoza, and Guanzon's filling of the third seat made the COA an all-women-led agency.

Days before retirement, Guanzon publicly named fellow commissioner Aimee Ferolino as "the one delaying the decision in favor of Marcos" before leaving the post.

Guanzon's assumption of her position as P3PWD representative was halted by a temporary restraining order by the Supreme Court taking action on the petition of Ronald and Ducielle Marie Cardema of the Duterte Youth.

[20][21] In 2024, the Supreme Court barred Guanzon from taking her congressional office by nullifying her nomination, citing grave abuse of discretion by COMELEC in approving her substitution past the designated deadline.