McAllan is a former corporate solicitor, who also served as a special advisor to First Minister Nicola Sturgeon prior to her election to the Scottish Parliament.

[3] Her father Ian is also a politician who has served as a local councillor for South Lanarkshire's Clydesdale East ward (which covers Biggar) since 2017.

[3] Before entering politics, McAllan co-founded human rights organisation RebLaw Scotland, which aims to use the law as a tool in the fight for social justice and held its first conference in 2017, worked as a corporate lawyer specialising in energy and natural resources and was a voluntary director of East Ayrshire's Women's Aid.

[4][5] She stood unsuccessfully in Dumfriesshire, Clydesdale and Tweeddale at the 2017 United Kingdom general election, where she came second to Conservative incumbent David Mundell.

In a subsequent Freedom of Information request made by the Daily Mail, the government were unable to provide the names of the world leaders as it did not retain such data.