Vallejos became a member of the Argentine national team during a historic period for the team: She helped the team qualify for the 2003 FIFA Women's World Cup, played in the United States. It was the first time that Argentina reached the World Cup on the women's side. During transmission of that tournament, Mexican women's national team player Fatima Leyva described Vallejos as the friendliest member of the Argentine women's national team.
She also participated at the 2003 Dominican Republic Pan American Games.