Partly the reason is that there are very few actual primary sources for her husband Abraham on his profile.
Here is the 1860 census for A. W. Venable of Granville County and his wife J. A. Venable, age 52 (thus born about 1808), native of North Carolina.
And here (sorry, ancestry.com record, haven't found it at familysearch.org) is the 1850 census record for A. W. Venable of Granville Couhty's wife J. A. Venable, age 43 (thus born about 1807), native of North Carolina.
Newspapers.com has the 1876 obituary (from the Torchlight of Oxford, NC) for Mrs. Isabella A. Venable, "widow of the late Hon. A. W. Venable", who died 14 Apr 1876 at the home of her son, Maj. T. B. Venable, age 69, and had been married 52 years (this implies a birth about 1807 and a marriage about 1824). A longer obituary from the next number of the Torchlight notes that she was the daughter of Thomas Brown, Esq., of Auchlochan, County Lanark, Scotland, "and was descended from Presbyterian Covenanters". She had been married nearly 53 years (thus the marriage was in 1823 rather than 1824) and survived her husband by a mere 8 weeks.
She had made out her will (at ancestry.com) on 9 March 1876; it was probated 16 June 1876.