Age 27 at time of marriage, of 21 Lyon Street, a bookkeeper.

She is presumably the Ellen Allerby who is shown in the 1900 Census as living at the same address as the Garvey family, 1298 Dorchester Avenue, age 13, born in February 1887 in Massachusetts. Birth records show a Nellie Allerby born 17 February 1888 at 1280 Dorchester Avenue to John A. and Mary C. Allerby, he a car driver born in England and she born in Dorchester. The birth record matches the census record with the exception of the year of birth of Ellen/Nellie and John A. is by 1900 an attorney rather than a driver.

1930 census:
They own a home at 254 Adams Street, Dorchester
Thomas M Garvey 40
Helen G Garvey 40
John I Garvey 14
Mary C Garvey 10
Thomas F Garvey 9
Helen G Garvey 6
Anne E Garvey 2 [9 4/12] 
Regina T Garvey 0 [11/12] 
Oliver W Holmes 38

Helen’s mother is shown renting at 252 Adams Street, a widow, age 65, with daughter Anna, unmarried, age 37, and Mary’s niece, Lilly, age 32 unmarried.