There are some details available for the Mary Sexton from Mallow...

Age 24; domestic servant; last residence was Mallow; she had been to the US 1 time before, earlier in 1894, to Quincy MA (I can't locate that record); she was visiting a cousin, Mrs. Buckley at 16(looks like 16, could be 10) Quincy Ave, Quincy, MA.

She was travelling with a Julia Sexton, age 18, who also has Mrs Buckley listed as a cousin; and Ellen Walsh, age 18, who has Mrs Buckley listed as a sister.

In the 1894 Quincy Directory, the only Buckley living on Quincy Ave is John Buckley, "coachman 15 School, h. 10 Quincy Ave". The 1901 Directory shows him living at 2 Franklin, still a coachman at 15 School.

From the 1900 Census then, at 2 Franklin...
1900 United States Federal Census
about John Buckley
Name: John Buckley
Home in 1900: Quincy Ward 3, Norfolk, Massachusetts
Age: 40
Birth Date: 1860
Birthplace: Ireland
Race: White
Ethnicity: American
Immigration Year: 1880 [I think it was 1890]
Relationship to head-of-house: Head
Father's Birthplace: Ireland
Mother's Birthplace: Ireland
Spouse's Name: Bessie
Marriage Year: 1893
Marital Status: Married
Years Married: 7
Residence : Quincy City, Norfolk, Massachusetts
Household Members: Name Age
John Buckley 40
Bessie Buckley 30
Katharine Buckley 5
May S Buckley 3
William Buckley 1

From NEHGS Quincy Vol: 434 ; Page: 497
Nov 16, 1893 in Boston, John Buckley, residing in Quincy, age 32, Coachman, born in Ireland, parents William and Margaret - m - Bridget Walsh, residing in Boston, age 28, Dressmaker, born in Ireland, parents William and Mary.

I tried to find a marriage or death record for Julia Sexton that would match the parents of Mary, but no luck with that.

Anyway, you can decide if this all matches up with that you already have.

John