Have you seen these?
1920 Federal Census, she gives her birthplace as New Townland, OC.
Source: Year: 1920; Census Place: Kent, Putnam, New York; Roll: T625_1256; Page: 1A; Enumeration District: 194; Image: 420.
NYS 1915 census, they are living with mother-in-law, Louise Dahl. Usually that means she is m-i-l to head of household, George but see 1910 census.
Source: New York State Archives, Albany, New York, State Population Census Schedules, 1915; Census Place: Election District 10, Assembly District 01, North Hempstead, Nassau, 10.
1910 Federal Census, mother (?) Louise Dahl and a niece with them.
Source: Year: 1910; Census Place: West Brookfield, Worcester, Massachusetts; Roll: T624_630; Page: 9A; Enumeration District: 1840; Image: ; FHL microfilm: 1374643
BUT, the 1900 census indicates Louise is George's mother; George is a widower.
Source: Year: 1900; Census Place: Manhattan, New York, New York; Roll: 1120; Page: 2B; Enumeration District: 0890; FHL microfilm: 1241120
Death records often list maiden names and burial places. Elizabeth is a widow in 1940. These are death indexes from IGG:
Jan 15 1931
Jul 7 1933
Apr 26 1934
Oct 14 1932
Marsh George W
Nov 5 1939
Feb 23 1947
Sep 8 1948