According to her Familysearch.org profile, her name may have been Isabel Armstrong. Fetterly-28 08:36, 28 February 2021 (UTC)
"Maine Vital Records, 1670-1921," database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:2H28-F5F : 4 April 2020), Isable Webster in entry for John Webster, 06 Sep 1726; citing Portland, , Maine, United States, multiple sources, Maine; FHL microfilm.
Proof of maiden name: History and Genealogy of the Stackpole Family (pub.1920) - page 138-139, 1920. History and Genealogy of the Stackpole Family (pub.1920) - page 138-139. Please note that this book was written long before the internet and easy access to birth, marriage and death records and is just used as a starting point for family research. There are many errors as to names and dates that show up when finding the online documentation for certain people. Image located at Ancestry.com.