Fernandes won the European Triathlon Championships five consecutive years (5 elite and 3 under-23 titles), beginning in 2004, and on 1 September 2007, she became world champion for the first time, in Hamburg, Germany, managing to grab the only title (apart from the Olympic sceptre) missing from her career.

She competed for her local triathlon club Clube de Perosinho and then for Belenenses where she became world champion of under-23.

On the second Olympic triathlon competition, at age eighteen, she finished in eighth place with a total time of 2:06:15.39.

[2] In September, she equaled Australian Emma Carney's record number of consecutive wins in the World Cup, with a twelfth victory at the Beijing leg.

Later that year, she was awarded with the "Best Female Athlete of the Year" prize from CNID (Clube Nacional de Imprensa Desportiva; English: Sports Press National Club) at its annual sports gala.