The name Isabella comes up on an old Adair chart, but I do not know whether she is connected with your particular lineage.
Rev. Patrick Adair of Carrickfergus married (c.1700) Isabella Adair, dau of Robert Adair and Rachel Forbes.One of Rev.Patrick & Isabella Adair's daus, Anne m. Rev. Anderson, minister of Kirkmaiden and they had dau. Isabella who d. 1770. This Isabella had married Hugh Nevin.