She was elected to the Victorian Legislative Assembly as a Liberal Party member for South-West Coast at a by-election held on 31 October 2015.
She was re-elected at the 2018 Victorian Election and appointed to Michael O'Brien's opposition front bench as Shadow Minister for Rural Roads and Shadow Minister for Ports and Freight.
Britnell attended St Ann's College in Warrnambool, and trained as a nurse at Warrnambool Base Hospital.
She worked as a nurse for almost 30 years and spend 15 years working in community health at the Framlingham Aboriginal Community.
Prior to her election Britnell was the vice-president of United Dairy farmers of Victoria, chairwoman of WestVic Dairy and was a Nuffield Farming Scholar in 2011.
Britnell also served on a number of number of boards including the Geoffrey Gardner Foundation, Glenelg Hopkins Catchment Management Authority, Australian Dairy Farmers Federation, was policy Councillor with the Victorian Farmers Federation, was a member of the Great South Coast Group’s Economic Pillar and a committee member of the Warrnambool City Council’s Food and Agriculture into China project.
She was named Victorian Rural Woman of The Year in 2009 and was named Australian Rural Woman of the Year in the same year