Her birth record on familysearch.org (in “Scotland, Births and Baptisms, 1564-1950”) shows her name as “Eliza Inches Blair”. It also has the information on her christening, and her parents names.
Her marriage listing on familysearch.org shows her name as Eliza Blair, so it is possible that Isabella is her middle name. Also, there is a record (in “Scotland, Births and Baptisms, 1564-1950” of an Eliza Inches Blair, born April 6, 1828 in Kettins, Angus, Scotland (same province her husband John as from), that lists her parents names as Andrew Blair and Grissel Douglas. Since John and Eliza named a son Andrew Blair McNabb, there is a strong chance that this is her.
1881 census listed as Isabelle McNab, widowed, born in Scotland. Living with her are James, John, Jane (no ages listed), Andrew (age 11), William (age 7), Eliza (age 2).
1891 census (with last name spelled McNab) -(S. Dufferin subdistrict, District East Selkirk, pages 32-33) shows that she was born in Scotland. It lists here name as Eliza. Since she was widowed at the time, her son John (as well as his wife and eldest daughter, Mildred “Jean”) and the rest of her kids were living in the same household.
Another reference has her listed as Eliza, but the 1881 census also shows her as Isabella.
The 1906 census shows her living with her daughter Eliza’s family, age 75 and widowed, but with the first name Eliza. It also says that she immigrated to Canada in 1863.
Her obituary from the November 10, 1910 Morden Chronicle newspaper:
DEATH OF A PIONEER - One by one the old pioneers are being called to their reward. Tuesday morning at 8 o’clock the soul of Mrs. John McNabb, sr., wafted away to be near its Maker. Deceased, who died at the home of her son Andrew, near Thornhill, had reach the advance age of 82 years, 7 months and 9 days. Mrs. McNabb with her husband came to this district from near Seaforth, Ont., in 1877, settling near Thornhill. During her long residence in the neighborhood Mrs. McNabb formed many strong friendships, and also saw many changes take place. About three years ago Mrs. McNabb fell, breaking one of her lower limbs and never recovered from the effects of the injury. For the past year she has been confined to her bed. Internment will take place today in Knightcote cemetery, Rev. H.J. Borthwick, A.M., an old friend of the family, conducting the services. Three sons and four daughters are left to mourn her loss, her husband predeceased her in 1879. The family are John and Andrew, near Thornhill, William at Asquith, Sask, Mrs. John Cowan, Thornhill, Mrs. Hallan, Okanagan, B.C., Mrs. H. Boyle, Saskatoon, and Mrs. Pepper, Manitou.