The marriages index at
www.scotlandspeople.gov.uk lists the marriage of William Suttie Duncan to Betsy Forbes Gillan (not Gill
ian) in 1939 in St Clement (Dundee).
There is a birth of Elizabeth Gillan Duncan, mother's maiden surname Gillan, in 1944 in the births index in Lochee. There are three other births of Duncan, mother's surname Gillan, in the index, but one is in 1878 and the other two can be accounted for by another Duncan/Gillan marriage.
Elizabeth Gillan Duncan, other surname Craig, 49, died in Dundee in 1993, mother's maiden surname Gillan. There is a matching marriage in 1969 in Dundee, but I can't post details as the husband could still be living.
So I think the answer to your question is that William Suttie Duncan and Betsy Forbes Gillan had only one daughter, Elizabeth (1844-1993).