Bessie put up a post yesterday on Ancestral Ties about the identity of the woman mentioned in the story of John Morgan's dream.
Here is her post complete with links: John Hamilton Morgan and Serepta M. Heywood.
Here is Serepta Blodgett Heywood's Findagrave entry. Her gravestone says "A Most Perfect Woman," which matches her role in the John Morgan story.
Here is the Heywood family website. Serepta's husband was Joseph Leland Heywood, and he spent much of his life in Utah living in Southern Utah.
There is not a picture of Serepta available online or at the Daughters of Utah Pioneers Museum. Her husband's diaries are available at the Trails of Hope: Overland Diaries and Letters, 1846-1869 database.
And an additional note: there is a chance that the story of John Morgan's dream, as later told by others, was a combination of two different stories about his mission in the Southern States.