Was Myrtle born around 1877? If so she possibly was the daughter of Henry Lewis Donham (b 1844) and Rachel Lodema Hale (b 1847) and is in the line that descended from Francis Singletary (b abt1550) through Nathaniel Donham and Keziah Crosley.
The Donhams are amazingly well-documented; there were two major Donham/Dunham families in the American Colonies in the 1600s and both appear frequently in records of the time. In working on my tree I discovered that I knew more about Jonathan Donham and his antics in the 1700s than I did about my own grandfather.
(BTW I grew up in Seelyville, nearby to Riley and Terre Haute)