Bancroft has a long history of involvement in community activism and arts administration, and has served as a board member for the National Gallery of Australia.

[3] She was the youngest of seven children of Owen Cecil Joseph Bancroft, known as "Bill"—an Aboriginal Australian from the Djanbun clan—and Dot, who is of Scottish and Polish ancestry.

[1] Following her father's advice on the importance of getting an education or a trade, Bancroft completed high school in Tenterfield before moving to Canberra in 1976 with her husband-to-be Ned Manning, who had also been her teacher.

[15] Described as "an instinctive colourist", Bancroft has since worked primarily as a painter, and has developed "a glowing style reminiscent of stained glass windows".

[18] In 2004, Bancroft was commissioned to design a large mural covering the exterior of a sports centre housing two basketball courts at Tempe Reserve in Marrickville, New South Wales.

[15] Bancroft ventured into illustrating children's books in 1993, when she provided the artwork for Fat and Juicy Place written by Dianna Kidd.

[20] Bancroft has since contributed artwork for over 20 children's books, including some by prominent Australian writer and artist Sally Morgan, whom she regards as a mentor and friend.

[12] Researcher and museum curator Margo Neale has described the art of both Bancroft and Morgan as depicting "their relationship to country and family in generally high-keyed works, celebrating and commemorating through personal or collective stories in mainly figurative narratives.

It simply and exquisitely rejoices in telling a story of this magnificent, sacred land we share: the mountains, rivers and gorges; seas and coral reefs; grasslands and bushlands; saltpans and snow; houses and streets; the jeweled night sky, and so much more.

[7][2] In the lead-up to the 2000 Summer Olympics in Sydney, Bancroft was a member of the design committee that advised on the development of the games' official logo,[32] and has acted as a judge for the $35,000 Country Energy Art Prize.

[33] Bancroft was a member of the board of directors of the Australian copyright collection agency, Viscopy, and while serving in that position has been an advocate of resale royalty rights for artists.

Her painting Prevention of AIDS (1992) was reproduced on posters and postcards aimed at raising awareness of HIV/AIDS,[39] and was one of several of her images commissioned by the federal Department of Health to highlight issues regarding the disease in the Indigenous community.

[42] She has taught and mentored Indigenous school students such as Jessica Birk, a winner of the Australia Council's inaugural Emerging and Young Artist Award in May 2009.

[46] Bancroft was appointed a Member of the Order of Australia in the 2024 King's Birthday Honours for "significant service to the arts, and to the Indigenous community".