Although the date of birth of her husband is known to be 1545, it is difficult to use that date as a basis of her birth although it is tempting to assume she was younger and therefore her birth was after 1545. It is known that she died in 1580 and had had four children by that time. With a minimum age of 12 and assuming one year for each child, one can infer her birth before 1566. It is admitted that most women did not marry at such a tender age with an average closer to 25 and that would place her birth closer to or before 1553 and closer to the age of her husband, but it is often better to make a certain statement rather than one that is conjectural leaving one with 'before 1566.' [Note too, her father died in 1572]
Sources
↑ 1.01.11.21.31.41.51.6
Welford, Richard, "Men of Mark 'Twixt Tyne and Tweed", London, Walter Scott, Ltd., 1895, Vol I, Google Books,
p. 73
↑ 2.02.12.22.32.42.5
Welford, Richard, "History of Newcastle and Gateshead", London: Water Scott, 1887, Google Books,
p. 170
Here is a transcript of her tombstone in Newcastle Cathedral;
"Here Lieth buried the corpes of Isabel Anderson late Wyf of Henry Anderson marchant and Alderman of this towne Who deceased the vid. daye of august an dni 1582 Bewailed of the poor that tasted much her renowined vertue."
Retrieved from a book in my collection;
Richardson, M. (1820). "A collection of Armorial Bearings" (Vol. 1)
"Here Lieth buried the corpes of Isabel Anderson late Wyf of Henry Anderson marchant and Alderman of this towne Who deceased the vid. daye of august an dni 1582 Bewailed of the poor that tasted much her renowined vertue."
Retrieved from a book in my collection; Richardson, M. (1820). "A collection of Armorial Bearings" (Vol. 1)