Mihychuk was born in Vita, Manitoba, the daughter of Katherine Salamandyk and Métro Mihychuk. She received the degrees of Bachelor of Arts from the University of Winnipeg in 1979, and Master of Science from Brock University in 1984. She is certified as a Practicing Professional Geoscientist. Mihychuk worked as a geologist in Newfoundland and Labrador from 1984 to 1986 and in Manitoba from 1986 to 1992. In 1992, she married Kenneth Marshall. She has two daughters, Sarah Mihychuk and Hannah Mihychuk, and a son, John. Mihychuk was first elected as a Winnipeg School Division Trustee first in 1989 and was re-elected in 1992.
Mihychuk resigned from cabinet and the legislature on May 21, 2004, to seek election as Mayor of Winnipeg. The 2004 election was held to determine the successor to former mayor Glen Murray. Murray had resigned to seek election to the House of Commons of Canada. Mihychuk's campaign platform focussed on increasing Winnipeg's population. Mihychuk lost this election, winning ten percent of the municipal electorate's vote. In 2005 Mihychuk relocated to Toronto, Ontario to work for the Prospectors and Developers Association of Canada as Director of Regulatory Affairs. Mihychuk supported Lorne Nystrom's campaigns to lead the federal New Democratic Party in 1995 and 2003.
Federal politics
In 2014, Mihychuk was chosen as the Liberal candidate in the riding of Kildonan—St. Paul for the 2015 federal election, defeating the previous Liberal candidate, Victor Andres. Mihychuk said that her views on the economy and social views were closer to those of the federal Liberals. She was subsequently elected to the seat. She was the Minister of Employment, Workforce, and Labour from November 4, 2015, until a cabinet shuffle in January 2017. She was accused of being abusive and causing confusion by the Canadian Red Cross after visiting a shelter for evacuees from forest fires affecting Garden Hill First Nation in 2018, a formal complaint was filed against her to the federal government. She was accused of adding to the chaos and suggesting to evacuees that they should go to Selkirk, Manitoba, and on her advice 40-50 evacuees waited in the cold with their belongings for transportation to Selkirk that never arrived. Indigenous people had requested her assistance because the Red Cross was ignoring them and placing families in large centre mixed in with a population that had people convicted of sexual offenses. Mihychuk pushed the Red Cross to treat the evacuees with respect and only after advocating were the large centres closed down and the evacuees placed into hotels. While Red Cross officials were upset, the evacuees expressed their satisfaction with the outcome to Indigenous MP Robert-Falcon Ouellette.
