Fernández won the Miss Venezuela 2008 title during a pageant held in Caracas, Venezuela on September 10, 2008. She was crowned by the outgoing titleholder, Dayana Mendoza, Miss Venezuela 2007 and Miss Universe 2008. Fernández also won the “Miss Elegance”, “Best Body” and “Best Face” titles.
She became the second Miss Trujillo to win that title since the Miss Venezuela pageant began in 1952. The first was Bárbara Palacios, Miss Venezuela 1986 and Miss Universe 1986. Stefanía is of Ukrainian, Galician and Polish origins. She plays tennis and swims as a hobby.