The marriage record indicates she was born in Durham Township, not Durham County, which would suggest Durham, Grey County, not Durham County east of Toronto. The marriage record would tend to be more correct as she likely gave the information vs. the death record where the informant may not have been as knowledgeable.
There are Aldreds in Bentinck Township (where the town of Durham is located) who are baptizing their children in the 1860s:
Notably there are also Aldreds in Clarke Township (where Port Hope is located) on the same list.
Effie is likely also a short name for something else. An online family tree has her parents as Henry & Catherine, with a number of siblings, born from 1849 through to Effie in 1874, which is a long time. Her mother, Catherine McInnes, born 1823, would have been 51 at the time of Effie's birth. Not unheard of, but certainly late in life.
Two other children of Henry & Catherine named Frederick & Henrietta also marry in Kent County in 1885 and 1886, so some or all of the family must have moved there.
1871 Canadian Census
Scugog, Reach Township, Ontario County
Aldred, Henry, aged 55, born England, Church of England, farmer, married
Aldred, Catherine, aged 47, born Scotland, married
Aldred, Joel, aged 18, born Ontario
Aldred, Benjamin, aged 15, born Ontario
Aldred, Ester Ann, aged 13, born Ontario
Aldred, Caroline, aged 11, born Ontario
Aldred, Frederick, aged 9, born Ontario
Aldred, Henrietta, aged 6, born Ontario
Aldred, Fanny, aged 3, born Ontario