[1] She is known for her role as Detective Sergeant (later DI) Alison 'Tosh' McIntosh in the BBC crime drama series Shetland (2013–present).
She initially studied international law at university but dropped out after three months to take up acting.
[1] Early in her acting career O'Donnell mainly worked in theatre, featuring in productions of Boys, The Hard Man, Eigengrau, and Yerma.
[2] She had small roles in BBC television productions Feel the Force (2006) and Holby City (2012).
[1] From 2013 to present, she has appeared in the main role of DS Alison 'Tosh' McIntosh, in the Scottish television crime drama Shetland made by ITV Studios for the BBC.