to Parliament after various party colleagues had resigned from Parliament to serve in the Basque Government. She was a member of the Basque National Party's parliamentary group. She was re-elected in the 2005 Basque Parliament election. She was briefly a member of the Basque Solidarity parliamentary group from 2005 to 2006, later re-joining the Basque National Party's group. She was the vice president of the Social Affairs and Employment Committee, and was one of the main promoters of the Families Support Law (2008) and the Social Servicies Law (2008). She was once again re-elected in the 2009 Basque Parliament election. During her three terms in the Basque Parliament, Mendoza became a prominent member of her party. She was tasked with the coordination of the parliamentary group, and was the spokesperson of the party in social policy issues. In June 2011, she stepped down from Parliament upon being elected to the General Assembly of Gipuzkoa. Member of the General Assembly of Gipuzkoa (2011-2019) Mendoza contested the 2011 Gipuzkoa foral election as the leading candidate of the Basque National Party in the Bidasoa-Oiartzun constituency. EAJ-PNV lost the control of the Gipuzkoa Provincial Council (the governing body of Gipuzkoa led by Markel Olano from 2007) after Bildu's electoral success. She was the first vice president of the General Assembly of Gipuzkoa (the legislative body) during the 2011-2015 term, as well as the spokesperson of the Social Policy Committe. She was a leading member of her party, tasked with the coordination of the parliamentary group, as well as EAJ-PNV's spokesperson on social policy issues. Mendoza was also a usual panellist in the media, representing her party. She was re-elected as a member of the General Assembly in the 2015 Gipuzkoa foral election. The Basque National Party was the most voted party, and Mendoza was named the president of the General Assembly for the 2015-2019 term. Gipuzkoa Provincial Council (since 2019) She was re-elected in the 2019 Gipuzkoa foral election, which saw EAJ-PNV increase the vote share and the number of seats. Mendoza was tipped to continue as the president of the General Assembly. However, the president of the Gipuzkoa Provincial Council, Markel Olano, incorporated her to his cabinet. Mendoza was named Provincial Deputy of Governance, as well as the spokesperson of the Provincial Council. In November 2020, president Olano reshuffled the cabinet and appointed Mendoza first vice-president. The reshuffle raised Mendoza's profile in government,