In 1986, she joined Spain's national junior rhythmic gymnastics team, where she was coached by Rosa Menor, Cathy Xaudaró and Berta Veiga.

Shortly after, she and the other members of the group (Beatriz Barral, Bito Fuster, Lorea Elso, Arancha Marty and Vanesa Muñiz, with Marta Aberturas and Nuria Arias as substitutes) won three bronze medals at the World Championships in Sarajevo.

[5][6][7][8][9] At the end of the year she won All-Around bronza at the Wacoal Cup in Japan, her last competition with the national team.

[10][11] Blanca, for her rope routine during la Liga Iberdrola, used a leotard that Mari Carmen wore during the World Championships in Sarajevo.

[12] After Boneva's death on 20 September 2019, Mari and other former national gymnasts gathered to pay tribute to her during the Euskalgym held on 16 November 2019.