Fagan was born in 1977[4] and grew up in Scotland within the Scottish Local Authority care system.[5] As a child she was adopted twice but neither placement worked out well.[6] She spent six years living on a caravan park,[6][7] and states that while she was a child she moved 26 times.[4] After leaving the care system, Fagan was also homeless for several years, living in homeless accommodation.[8]
With the publication of her first novel in 2013, Fagan was listed by Granta as one of the 2013 Granta Best Young British Novelists.[10]The Panopticon was well received in the press, with The New York Times describing her writing by saying: "...there is no resisting the tidal rollout of Fagan's imagery. Her prose beats behind your eyelids..."[11] and also describing Fagan as The Patron Saint of Literary Street Urchins."[12]
Her second novel, The Sunlight Pilgrims released in 2016, tells the story of a transgender young girl named Stella who lives on a caravan park and is based around the relationships she forms while growing up, set against a backdrop of rural Scotland during a period of freezing climate change. Writer Ben Myers described it as "prose that sparkles from the first page."[13]
Fagan mentors young writers and works with young people including offenders and those in the prison system. She curated an art exhibition at Tramway in Glasgow entitled Narrative for Koestler Trust in 2017. It showcased artwork by prisoners, young offenders and those in secure psychiatric care from all across Scotland.[15]
In 2017, as part of the Edinburgh International Book Festival, Fagan and four other Scottish writers took part in the Outriders Project, which involved taking road trips across the continent of America with local writers to explore partnerships while writing and blogging throughout the journey. Fagan's journey entailed travelling from the Rust Belt to Silicon Valley where she explored "questions on the nature of truth." She was accompanied by American novelist Bonnie Jo Campbell.[16] The subsequent novel length poem called TRUTH was published by Tangerine Press in Autumn 2019.[citation needed]
It was during a writing residency at Shakespeare and Company, in Paris, she wrote some of the poetry which made up her poetry collection There’s a Witch in the Word Machine.[17]
She directed her first short film in 2018, a cine-poem about Bangour Village Hospital where she was born. She has also experimented with other media such as sculpture when she created a giant metal scold's bridle onto which she engraved words by women prisoners from the UK and USA, including submissions from women on death row.[8]