Born in British Hong Kong, Baillie was educated at St Anne's School, Windermere before studying at Cumbernauld College and the University of Strathclyde.

She again served as acting Scottish Labour leader for six weeks following Leonard's resignation in January 2021 and has been described by journalist Alex Massie as someone "who both loves to wind-up the SNP and is good at it".

After education at the private St Anne's School, Windermere in the Lake District, she studied at Cumbernauld College and the University of Strathclyde.

[7] In 2009, Baillie successfully brought into being an act of the Scottish Parliament, with the unanimous support of all MSPs, to allow for greater protection of disabled parking spaces.

[15] Baillie ruled herself out of standing in the leadership election that followed Lamont's departure, stating that she wanted a "supporting role" rather than to be Labour leader.

[16] As a backbench MSP, Baillie campaigned for a public inquiry into a lethal outbreak of Clostridioides difficile infections at the Vale of Leven Hospital in her constituency.

Baillie continued to serve as Scottish Labour Spokesperson for Economy, Jobs and Fair Work until October 2018 when she was sacked by Leonard, who also replaced her in the role.

In January 2020, Baillie announced that she would be standing as a candidate for the post of Deputy Leader of the Scottish Labour Party.

"[26] In the run up to the 2021 Scottish Parliament election, former SNP Depute Leader Jim Sillars donated £2,000 to her campaign to be re-elected.

"[27] Ballie was re-elected in May 2021 with an increased majority of 1,483, with Dumbarton becoming the only seat to have voted Labour for the entirety of the devolved era.

"[29] Baillie was appointed Dame Commander of the Order of the British Empire (DBE) in the 2023 Birthday Honours for political and public service.

During her time as MSP, she studied for a Master of Science degree in Local Economic Development at the University of Glasgow.