Delgado joined the Public Prosecution Service in 1989, being assigned to the High Court of Justice of the Autonomous Community of Catalonia.

The motion, at People's Party initiative, considered that Delgado should not continue in the office because of her "perverse friendships" with the retired police commissioner José Manuel Villarejo and the former National Court justice Baltasar Garzón.

[8] A month later, on 22 November 2018, the Congress of Deputies requested her resignation again for urging the State Lawyers Corps to rule out the crime of rebellion to jailed Catalan separatist leaders.

[9] On 24 October 2019, she was one of the representatives of the caretaker government in the exhumation of Francisco Franco, serving as First Notary of the Kingdom, attesting to the incidentless extraction of the coffin with the remains of the dictator.

After the Sánchez II Government was sworn in, the Council of Minister nominated her on 13 January 2020 as the next Attorney General, succeeding María José Segarra.

[13] Despite criticism from the opposition parties and some conservative prosecution associations to her nomination,[14][15] the Plenary of General Council of the Judiciary (CGPJ) on 16 January 2020 approved her candidature by 12-7 votes.

Among her statements, she denied that having been a minister was a cause for not being appointed attorney general:[19] My time in the Ministry has been a factor that has enriched my profile, giving me an overview of the justice system, a deep knowledge of its actors, an international vision and great experience in the formation and management of work teams (...).