Born in la Seu d'Urgell in 1963.

She holds a degree in Law from the University of Barcelona.

She has been a practising lawyer since 1988, and is a member of the Barcelona Bar Association. She was president of the Catalan Association of Democratic Lawyers (2003-2007). She was manager of the Barcelona Municipal Institute for People with Disabilities. She is a member of various women's associations: Dona i Drets, the Association for the Support of the Women's Lobby of Catalonia and Themis. She is also a member of Òmnium Cultural. 

In her institutional career, Capella was, until recently, the head of the Catalan Government Delegation in Madrid. From 2018 to 2021, she was Minister for Justice, the ministry from which she promoted the Law on rent containment in housing lease contracts. Previously, she was an Esquerra Republicana member of the Catalan Parliament (2021), ERC deputy in the Congress of Deputies (2015-2018), senator appointed by the Catalan Parliament (2013-2015) and ERC spokesperson for Barcelona City Council (2007-2011).