Hemphill was the daughter of James Leroy Miller and Elaine Agnes McParlor, born in Grand Forks, British Columbia, and was educated at Bralorne. She served on the Assiniboine South School Board[2] in 1969, 1970 and 1973.[3] She married H. David Hemphill but they had divorced by the 1980s.[4]
She first ran for the provincial legislature in 1977, in the southwest Winnipeg riding of Charleswood. She came a distant second behind Progressive Conservative leader Sterling Lyon, whose party defeated Edward Schreyer's New Democratic Party to win the election.[5]
The Manitoba NDP regained power under Howard Pawley's leadership in 1981, and Hemphill was easily elected for the north-central Winnipeg riding of Logan (former Mayor of Winnipeg Stephen Juba came a distant second behind her running as an independent candidate). Hemphill was appointed Minister of Education[6] on November 30, 1981,[7] and retained this position for the entirety of the Pawley government's first mandate. She increased state support for private and parochial schools while holding this portfolio, despite the NDP's historical objections to such funding.
Hemphill was re-elected without difficulty in 1986 (defeating future Liberal MLA Kevin Lamoureux) and was appointed Minister of Business Development and Tourism on April 17, 1986. On September 21, 1987, a cabinet shuffle made her the Minister of Community Services.[8]
After the Pawley government lost a parliamentary vote of non-confidence in 1988, Hemphill became a candidate to serve as the party's new leader.[8] She placed fourth on the first ballot, and gave her support to third-place candidate Andy Anstett, who was eliminated on the second ballot. Afterward, she supported Len Harapiak, who lost to Gary Doer.
Hemphill was re-elected in the 1988 Manitoba general election, albeit by a reduced margin. She was not a candidate in 1990.[1]
In 1993, Hemphill ran for the national New Democratic Party in the riding of Winnipeg North Centre, but placed second to incumbent Liberal David Walker.[9]
Hemphill died on February 22, 2026, at the age of 89.[10]