There are a few hits on Ancestry.com, but, as with Wikipedia, you need to look for documentation. A Google search on "Lady Devorguilla of Galloway" returned a few hits, but also suggested an alternate spelling of "Devorgilla." A lot of the hits were to sites talking more about historic places than about Lady Devorguill, but that can be interesting. There were also a nnumber of hits on "Google Books."

Good Luck