Usero took up the sport at Escuela de Gimnasia Rítmica of
Zaragoza. In 1982 she won bronze in the 2nd category of the
Spanish Championships in
Palencia. She became part of the Spanish national group, she would train at the Moscardó Gymnasium in
Madrid under the orders of the national team coach
Emilia Boneva and the group coach,
Ana Roncero, Georgi Neykov was the team's choreographer. In 1984 she won the bronze medal in the all-around competition at the
European Championships in
Vienna along
Pilar Domenech,
María Fernández,
Virginia Manzanera,
Eva Obalat and
Graciela Yanes, with
Rocío Ducay and
Ofelia Rodríguez as substitutes. After this achievement, they were all awarded the Medal of Gymnastic Merit of 1984 from the
Royal Spanish Gymnastics Federation that was given to them in 1985 in a ceremony presided over by
Alfonso de Borbón y Dampierre, Duke of Cádiz, then president of the COE. At the
1985 World Championships in
Valladolid the group was 7th in the All-Around along
Pilar Domenech,
Eva Obalat,
Ofelia Rodríguez,
María Fernández and
Graciela Yanes, in addition to Ester Domínguez,
Rocío Ducay,
Laura Manzanera and
Estela Martín as substitutes. After her retirement, she served as technical director of the Aragonese Gymnastics Federation and prepared gymnasts at her childhood club, eventually training
Esther Domínguez from 1994 until she was called by the individuals national coach
Mar Lozano. In 1997, Nancy was selected as head of the national junior group. In September 1998, she was named national head coach for groups, replacing
María Fernández Ostolaza. She had
Dalia Kutkaite as assistant and coach of the junior group, and Cristina Álvarez as choreographer the first year. During 1999 and 2000, the two exercises were with 3 ribbons and 2 hoops and the one with 10 clubs, in the first they used "Zorongo gitano" and "Babelia" by
Chano Domínguez, Hozan Yamamoto and Javier Paxariño for the second, as music during 1999. That year the group was made up of
Sara Bayón,
Marta Calamonte,
Lorena Guréndez,
Carolina Malchair,
Beatriz Nogalez and
Paula Orive. At the end of May at the
European Championships in
Budapest, they were 7th in the All-Around, due to a poor score in the 10 clubs exercise. In the 3 ribbons and 2 hoops competition they won the bronze medal. In August the team won the silver medal in the mixed event at the DTB-Pokal in
Bochum. At the end of September at the
World Championships in
Osaka they were 7th overall competition, which gave them qualification for the
Sydney Olympic Games the following year. Subsequently, they took 6th place in both event finals. In 2000 they had two new routines, now with music by Los Activos and
Vicente Amigo and, for the 10 clubs exercise, with a medley by
The Corrs and
Loreena McKennitt. In October 2000 Nancy Usero was renewed as head coach, position she would keep until March 2001, date on which she was replaced by
Nina Vitrichenko, who would be the head coach between March and September of that year. After Boneva's death on 20 September 2019, Nancy and other former national gymnasts gathered to pay tribute to her during the
Euskalgym held on 16 November 2019. The event took place before 8,500 attendees at the
Bilbao Exhibition Center de
Baracaldo and was followed by a dinner in Boneva's honor. == Legacy and influence ==