[6] Also under her leadership, Andalusia defied a 2012 ban on free healthcare for undocumented immigrants, imposed by the central government as part of spending cuts to avoid an international bailout amid the European debt crisis.

[10] Felipe VI sanctioned by royal decree of June her appointment as the first female holder of the portfolio of Minister of Treasury of Spain.

[12][13] By January 2019, Montero presented her minority government's first budget proposal of 472.7 billion euro ($543 billion), promising to reduce its deficit to 1.3 percent of gross domestic product but also increase social spending by over 6 percent;[14] the proposal failed to get parliamentary approval and instead prompted a snap election.

[17] Following recommendations from the International Monetary Fund (IMF) aimed at reviving the economy amid the COVID-19 pandemic in Spain, Montero led efforts in 2020 to suspend the constitutional commitment to any deficit targets for two years and allow the government to spend and borrow at will.

[21] In a letter sent to their counterparts in the European Commission – Pierre Moscovici and Miguel Arias Cañete – in May 2019, Montero and Environment Minister Teresa Ribera called on the European Union to assess a potential carbon tax on power imports to protect the bloc’s interests and help it to pursue its environmental targets amid growing public concern over climate change.