Do you know the names of any possible siblings or cousins of Rebecca Ann and if so, have you tried to follow their families (in case they may have named children after other Long/Porter family members)?
Summing up records, in case there might be clues...
1851 Stanley, York County, New Brunswick Census
James Fairley and Rebecca Ann (age 27) and their children
Mary Elizabeth, Sarah Ann and Charles
Rebecca was born in the colony; race: Irish. James was a farmer, lumberman?-Prop.
Apparently, also living in the dwelling were several lodgers, including a
John Long, age 24, race: Irish, Labourer, lived in colony since birth
Could John have been a brother or other relative?
1851 Stanley, York County, New Brunswick Census
George Porter, age 40, race: Irish, Farmer, lived in colony since birth
and his family Christie? and their children
Could George have been Rebecca's cousin?
1861 Stanley, York, New Brunswick Census
James Fairley and Rebecca (age 36), and their children
Mary E, Sarah A, Charlotte, Daniel, Joseph W, James ?, John C, Ernest A
James was a farmer and lumberman. James was ? Baptist and Rebecca was Methodist
Living near the family was a William Fairley (possibly James' older brother?), who was Methodist.
According to one online tree, the children's names were
Mary Margaret Elizabeth, Sarah Ann, Charlotte, Charles Leonard, Christine Adelaide, Daniel, Justus William, James Scott, John Cameron, Ernest Augustus, Martha Jean and Richard Everett.
Do you know of any Everett's in the families? Could Richard Everett have been named after a relative with the surname of Everett?