Name from another family tree. However, her year of birth fits, and she was living in Summerside at the time of her marriage.
But - she was not named in Isaac's will.
Groom's Name Peter Scott
Groom's Residence North River
Groom's Status Widow/Widower in some records, bachelor in others
Bride's Name Margaret Howat
Bride's Residence Summerside
Bride's Status Spinster
Source RG19/s3/ss5: Marriage bonds, 1867
Married in the presence of the bride's parents; married 4 dec 1867
Name Margaret Scott
Event Type Census
Event Date 1881
Event Place Lot 17, Prince, Prince Edward Island, Canada
Event Place Lot 17, Prince, Prince Edward Island, Canada
Age 46
Marital Status Married
Nationality Scotch
Race Scottish
Religion Bapt.
Birth Date 1835
Birthplace Prince Edward Island
Head of Household Name Peter Scott
Peter Scott M 46 Prince Edward Island
Margaret Scott F 46 Prince Edward Island
William Scott M 18 Prince Edward Island
Theodore Scott M 12 Prince Edward Island
John J. Scott M 10 Prince Edward Island
Walter Scott M 9 Prince Edward Island
Citing this Record "Canada Census, 1881," database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:MVN7-BXB : 4 October 2018), Margaret Scott in household of Peter Scott, Lot 17, Prince, Prince Edward Island, Canada; from "1881 Canadian Census." Database with images. Ancestry. (www.ancestry.com : 2008); citing Peter Scott, citing Library and Archives Canada, Ottawa, Ontario.