Chapman served as the Deputy Premier of South Australia and Attorney-General between 19 March 2018 and 22 November 2021 in the Marshall government.

She again tried to win preselection, this time for the safest Liberal seat in the metropolitan area, Bragg, located in Adelaide's wealthy eastern suburbs.

When sitting member Graham Ingerson resigned, Chapman contested preselection against Liberal minister Michael Armitage, who was seeking to move from his marginal seat of Adelaide.

Chapman easily gained preselection and retained Bragg with a slight 0.4-point two-party swing at the 2002 state election when the Liberals lost government.

Chapman immediately joined the front bench, assuming the shadow portfolios of Education and Children's Services.

[4] Despite having attempted to previously oust Hamilton-Smith as leader and having attempted to later defeat Redmond in a leadership ballot, Chapman voted for Hamilton-Smith in his successful bid as deputy leader on 31 March 2010 in a vote held after the third consecutive Liberal loss at the 2010 election where Chapman gained a substantial 9.1-point two-party swing.

[5] Chapman drew headlines in the last week before the 2010 election for not being willing to publicly refuse challenging Redmond for the leadership and faced accusations, particularly by Hamilton-Smith, of derailing the Liberal campaign, with "Chapman Could Challenge" posters hung beneath many of the Liberal "Redmond is Ready" posters.

[9] On 22 November 2021, she resigned as Deputy Premier and Minister for Planning and Local Government, and stepped down as Attorney-General while officially still holding the role and remaining in cabinet.

[12] Chapman retained her seat in parliament at the 2022 South Australian state election, despite a swing against her party which resulted in a change of government.