She was elected to the Northern Territory Legislative Assembly representing the division of Araluen for the Country Liberal Party in a 2010 by-election following the resignation of Jodeen Carney. In addition to running the business and raising two children, Lambley served as a councillor on the Alice Springs Town Council, and was deputy mayor of Alice Springs from 2006 to 2007. Following the Country Liberal Party"s victory in the 2012 territory election, the CLP voted Lambley deputy leader of the party (and Deputy Chief Minister to Terry Mills), replacing Kezia Purick who had been deputy leader prior to the election.
Lambley resigned as the Deputy Chief Minister on 5 March 2013, but was reported to be likely to remain the Treasurer.
Lambley was sacked from cabinet in February 2015 for helping Willem Westra van Holthe and John Elferink line up support for their attempted coup against Chief Minister Adam Giles. She resigned from the CLP on 17 June 2015 after the release of a proposed redistribution of electoral boundaries that would see her seat of Araluen dismantled.