Radio Patriot is reporting that one of her parents was an American.
Ancestry.com
http://www.wargs.com/political/granholm.html
Ancestry of Jennifer Granholm
1 Jennifer Granholm, b. Vancouver, B. C., Canada, 5 Feb. 1959, emigrated with her parents to US in 1962, naturalized ... [early 1980s], Governor of Michigan 2003-current
m. ... 23 May 1986
Daniel Mulhern, b. ... , son of ... Mulhern and of ... .
three children (Kathryn, Cecelia, Jack)
PARENTS
2 Victor Ivar Granholm, b. Penny, B. C., ...
m.
3 Shirley Alfreda Dowden, b. ...
Her mother wouldn’t have had to “emigrate” if she were an American. I seen no proof. It also depends on the law at the time of birth. The reason it’s important whether Obama was born in the U.S. is because of the law at the time, his mother was too young to have lived in the U.S. for the time requisite to confer citizenship on him.
If Granholm’s mother was a U.S. citizen, but didn’t meet the criteria, Granholm would have had to be naturalized.