Marjorie Charteris is not identified by name in the following record, but it would appear to be her who is mentioned in an exchequer account, which belongs to the year 1359, as the widow of the deceased Thomas Bruce: "sponse quondam Thome de Bruys."
Exchequer Rolls of Scotland. Vol. I A.D. 1263-1359. pp. 572-74.
https://archive.org/details/rotuliscaccariir01scot/page/572/mode/1up
That was certainly the opinion of the joint editors of volume I of the Exchequer Rolls of Scotland.
Exchequer Rolls of Scotland. Vol. I A.D. 1263-1359. p, cxxxiii note 3.
https://archive.org/details/rotuliscaccariir01scot/page/n138/mode/1up