Elizabeth married John McNab, son of Source of Kilbrandon/Kilchattan McNab and Unknown, on 30 Oct 1788 in Kilbrandon/Kilchattan, Argyll.1 (John McNab was born before 1760 in Argyllshire and died after 1841.)
Scotland's People - Document Image, www.scotlandspeople.gov.uk, OPR Marriages. 30/10/1788 MCNAB JOHN ELIZABETH MCDOUGALL/FR163 M KILBRANDON/ KILCHATTAN 515/00 0001 No Image
. I'm only guessing that this is our John's wife but the marriage does occur after the last of Agnes' known children.