The following information is from: Sandeman, G.L. (ed.) (1950) "The Sandeman Genealogy", Edinburgh: George Waterston & Sons Limited.
Page 6: "Robert Sandeman, b. 1718; d. 1771; buried at Danbury, Connecticut, U.S.A. (then New England); m., 1737, Catherine Glas, d. 1764 (no issue)."
Page 101 gives the following information which may help you find where Catherine died: "[Robert Sandeman] went to Edinburgh and in 1760 to London, where he ministered for some years. In 1764 he went to America (then New England), where he planted several churches..."
Please contact me by e-mail if you would like some biographical information on Robert Sandeman, or on the Glas family (i.e. Catherine's parents and grandparents) or further ancestral/family information on either of the two individuals.