Donna Jean MacKinnon was born June 3, 1943, in Cape Breton Island (Nova Scotia). She graduated with a B.A. in English and Near Eastern History from Victoria College at the University of Toronto. Subsequently, MacKinnon received a secondary school teaching certificate from the Ontario College of Education (OISE). After graduation, she worked as a social worker, teacher, barmaid, department store buyer, antiques dealer at Salmagundi and the Hudson’s Bay Company, and freelance writer.

From 1986 to 2009, MacKinnon worked as a staff reporter at the Toronto Star. While at the Star, MacKinnon wrote about a wide range of subjects, from entertainment stories, business (including the weekly column “Thinking Big”), home design and architecture (weekly section “Sunday Home”), and general assignment stories covering daily city news. During this time, MacKinnon also wrote as a freelancer for Condo Living (column titled “Best Laid Plans”), City & Country Magazine, the Globe and Mail, the Washington Post, the Toronto Life, House & Home, Great Expectations, and Canadian Jeweller. As a freelancer, she also wrote two scripts for T.V. Ontario and posts for the Presbyterian Record (blog "Recipes and Memories"). During her years as a reporter, MacKinnon published over 15,000 news pieces either under her name, the byline Isabella Street, and as a ghostwriter.

In the 1990s, MacKinnon started working on her book Newsgirls: gutsy pioneers in Canada’s newsrooms which she published in 2017.

MacKinnon is a certified yoga teacher registered with the American Yoga Teachers Association.