Romero has won world championships in both cycling and rowing; as a rower, she won a silver medal at the Athens 2004 Olympics in the quadruple sculls, and the following year was part of the British crew that won the 2005 World Championships in the quad sculls. Suffering from a persistent back injury, Romero retired from rowing in 2006.
Romero later took up track cycling, and made rapid progress in her new sport, specialising in track endurance events.
In December 2006, Romero won a silver medal in the pursuit at the UCI Track World Cup event in Moscow – her international cycling debut – losing out to fellow Briton Wendy Houvenaghel.
Romero won her first Cycling World Championships medal in March 2007 with silver in the 3 km pursuit. The following year, at the 2008 UCI Track Cycling World Championships, held in Manchester, she won the individual and, (with Houvenaghel and Joanna Rowsell), team pursuit events.