Her parents enrolled the talented young girl in dance lessons at which she excelled, although at her young age, she was already immensely competitive with the other dancers. At the same time, her mother was prompted to enter her into local beauty contests and she began competing competitively at age 10. By the time she turned 18 she was preparing for the Miss Argentina competition.

The competition between the contestants was at a fever pitch with numerous backstage altercations. The frenzied atmosphere came to a head when Rosario made it into the final five contestants. When Leticia Maldanado was named the 2nd runner-up, it left Rosario facing Paoula Vallez in line for the title. Maldanado, distraught over her third place finish rushed at the two finalists catching Delgado off guard, slapping her in the face and tearing off the top part of Rosario's dress.