On a message board posted by Dorothy Mack (12dorothy52631@comcast.net), Life Member, The Boone Society, she states Martha Farmer was Israel Boone's wife. She said this information can be found in "Boone Family To America 1670-1720" Volume II by Jim White. Israel Boone and Martha Farmer were married 31 December 1747 by Rev. John Marks.

As a side note, some believe Martha was a Lenape (Delaware) Indian.

Good luck on your search.