After serving 16 years in the Chamber of Representatives, Mejía ran for Senator of Colombia in the 2002 legislative elections as a Liberal candidate heading the Electoral List 648 that also included Ernesto Zuluaga Ramírez, Atilano Alonso Giraldo Arboleda, Miguel Ángel Pérez Gamboa, and José Albeiro Gallego Agudelo.
[3] In 2004, following a national debate about amending the constitution to allow for a second presidential term, a motion widely popular among Colombians and sought by the sitting President Álvaro Uribe Vélez, Mejía voted in favour of the re-election amendment and went against the official position of her party which opposed the re-elections of Uribe that demanded that all its members vote against it.
For her vote, Mejía and other eight Liberal Senators including: Luis Guillermo Vélez Trujillo, José Renán Trujillo García, Víctor Renán Barco López, Jorge Aurelio Iragorri Hormaza, Piedad del Socorro Zuccardi de García, Dilian Francisca Toro Torres, Manuel Antonio Díaz Jimeno, and Flor Modesta Gnecco Arregocés, were suspended by the Disciplinary Tribunal of the Liberal Party for a period of ten months each;[4][5] She was replaced in Congress on 28 August 2004 by Ernesto Zuluaga Ramírez, second-in-row of her electoral list.
[6] Born 16 March 1945 in Pereira, Risaralda, Mariza, as she is known to those close to her, is the daughter of Bernardo Mejía Jaramillo and Dora Marulanda Gutiérrez.
She completed her secondary education in Pereira and later attended Michigan State University where she graduated with a Bachelor in Economics, and later received a Master's Degree in Art History.