Gallagher made her television debut as Alicia Hodge in two 2009 episodes of the
BBC One medical soap opera
Doctors. Her early stage work includes
The Bloody Chamber and
The Wicked Lady in England, and
Be My Baby and
Sleep Eat Party in Belfast. She starred as the titular character in
The Haunting of Helena Blunden at the
Waterfront Hall. This was followed by
Dockers and
White Star of the North at the
Lyric Theatre, Belfast. She would return to the Lyric for
Weddins, Weeins and Wakes,
Demented,
Pentecost,
Stitched Up,
Little Red Riding Hood,
Love or Money,
Smiley, and
Bah, Humbug!. In 2012, Gallagher played Helena in ''
A Midsummer Night's Dream'' at the
Royal Lyceum Theatre in Edinburgh. The following year, she made her feature film debut in actor Paul Kennedy's 2013 directorial debut
Made in Belfast. She played DC Emer Taylor in the
BBC Two crime drama
The Fall. At the
Belfast Festival at Queen's, she appeared in
Belfast by Moonlight and debuted the play
The Holy Holy Bus, which she would return to. Her other stage work includes
Playhouse Creatures in Lisburn. Gallagher wrote her first play
Natural Disaster to process her grief over losing her father in 2017. After starring in ''
Abigail's Party at the MAC, Gallagher premiered her play there. She also returned to A Midsummer Night's Dream'', this time playing Hermia at Queen's Hall in Newtownards, went on tour with
Is That Too Hot?, and appeared in
The Real Housewives of Norn Iron at the
Grand Opera House. The following year, Gallagher returned to film in
Nowhere Special. In 2021, it was announced Gallagher would star in her first lead television role as Shiv Sheridan in the
BritBox and
RTÉ comedy-drama
The Dry, which premiered in 2022. She also appeared in the horror film
Mandrake and the television film ''St Mungo's
. She also appears opposite Johnny Flynn in the Sky Atlantic series The Lovers''. ==Personal life==