Manison was born in Tennant Creek, and she later studied journalism and public relations at Curtin University in Perth.

Prior to entering politics, she worked as human resources and communications manager for MG Kailis Group and as a media advisor to former Labor leaders Paul Henderson and Delia Lawrie.

Following Labor's victory at the 2016 election, Manison was sworn in as Treasurer of the Northern Territory on 31 August, replacing former Chief Minister Adam Giles.

[9] In April 2024, she signed a gas supply agreement with US firm Tamboran Resources, without a competitive tender process, and without divulging the costs.

[10] Less than three months later, she accepted a job with Tamboran, as vice-president of government relations and public affairs, leading to revolving door criticisms.