In 2016 Nievas, along with Rasta Rasivhenge, was jointly named World Rugby Referee of the Year.

As a child she spent time in Almería, where she played and tried out various sports including association football, tennis, basketball, volleyball, and karate.

[3][4][1][5] Nievas first began playing women's rugby union in 2002, aged 19, while attending the University of Málaga, where she was studying for a degree in telecommunications engineering.

She subsequently played for the university's women's team for ten years and also served as club captain.

In addition to playing for CDU Málaga, Nievas represented Andalucía at provincial level.

In 2012, after being offered the chance to take charge of matches in senior men's competitions, Nievas chose to retire as a player and concentrate on refereeing.

In 2014, after Paloma Loza and Itziar Díaz, she became the third woman to referee a Copa del Rey de Rugby final.

[5] On 19 November 2016 Nievas served as an assistant referee at an international between Tonga and the United States at Anoeta Stadium.