Wendy Machin was educated at Wingham High School and the NSW Institute of Technology (BA). After graduation, she worked as a Young National Party field organiser for a year and was Communications officer for the National Party of Australia 1981-2. She was elected to North Sydney Municipal Council in 1983, and in 1985 to the NSW Legislative Assembly for Gloucester, becoming the first woman to be elected for the National Party to the Legislative Assembly. Subsequently, she won the seats of Manning and Port Macquarie, and was MLA for Port Macquarie until her resignation in 1996, after the birth of her second child.

Wendy Machin was Chairman of Committees 1989-1993, Minister for Consumer Affairs, and Minister assisting the Minister for Roads from1993-5. She was Shadow Minister for Consumer Affairs, Roads and Fisheries 1995-1996. She was vice chairman of the Australian Republican Movement in 1998-2000 and was one of its delegates to the Constitutional Convention in 1998. She was President of the Save the Children Fund 1996-2000. In 2005 she was appointed by the Insurance Council of Australia to review their general insurance privacy code. Also, in 2005, she was appointed to the Board of the NRMA. She is a member of the Migration Review Tribunal.

She married David P. Bell on 20 July 1991, and they have one son, and one daughter. She owns and runs a beef cattle property near Wingham and runs her own consultancy business, Machin Consulting.