On November 23, 2007, Rivera represented Dorado at Miss Puerto Rico Universe 2008. Rivera advanced to the five semifinalist phase, along participants representing Isabela, Utuado, Trujillo Alto and Santurce. As part of a "final question" segment she was asked "With what social labor do you identify yourself and why?" to which she responded that she supported women that are victims of domestic abuse. Rivera advanced to the final two semifinalist spots along Santurce, and was selected the contest winner by a jury. Rivera and Puerto Rico's delegation were offered $25,000 in economic support for their preparation prior to Miss Universe 2008. In this pageant Rivera would wear dresses created by numerous designers including Carlos Alberto, René Cruz, Nathalia López, Chegüi Lacén, José Raúl, Antonio Da Silva, José Braulio, José Karlo, Ivanyo, Verona, Casanova, Machito, Pipo Pere, Adam Hernández, Valentino Zeliachi and Ángel Guzmán, with most of the pieces exhibiting brilliant colors representative of the tropical climate found in the Caribbean.
On November 25, 2007, two days after winning the 2008 Miss Puerto Rico Universe pageant, Rivera asserted that her competition gown and her makeup had caused a strange reaction on her skin. Pageant organizers claimed that someone had doused her personal items with pepper spray. On November 30, 2007, the island's Forensic Science Institute announced that no traces of pepper spray had been found on the garment or her makeup brushes, which had been submitted for testing by pageant organizers. However, FSI spokesperson Abigail Marrero did point out that the test was not conclusive. Nevertheless, during an on-air interview of the incident at San Juan's Channel 4 WAPA-TV, Police SuperintendentPedro Toledo stated that he would look into what he called false accusations as well as the possibility of pressing perjury charges. He said he would not tolerate the use of public resources for publicity purposes. A subsequent investigation by the FSI conclusively determined that someone had indeed doused Rivera's garments with pepper spray. Lt. Eddie Hernández, a Puerto Rico Police spokesman, stated on December 19, 2007, that "Miss Puerto Rico Universe was speaking the truth. She was being sincere about the allegations." Evidence has been forwarded to the district attorney's office for possible criminal prosecution.
Miss Universe 2008
On July 8, 2008, Rivera participated in Miss Universe's preliminary pageant, in the swimsuit and gala competitions, where she wore a dress composed of several golden metal rings. This stage also included an interview with the jury. Following the conclusion the preliminary stage, Rivera's parents joined her in Vietnam. Despite being considered a big favorite Rivera did not advance to the semifinals, which caused surprise among the local media as well as her family. Subsequently, she expressed satisfaction with her performance but also expressed disbelief for her elimination in the final stages of competition. Rivera returned to Puerto Rico on July 26, 2008. She subsequently noted that several work proposals had been presented to her, which were under consideration. Rivera was scheduled to attend Televisa auditions in November 2008, and was to move to either the United States or Mexico depending on the result.
