Deletion of Mamie Lincoln Isham

Comment: Lincoln's family is written about in depth in numerous |sources, such as Neely, Mark E., and Harold Holzer. The Lincoln Family Album. Doubleday, 1990. and Lachman, Charles. The Last Lincolns: The Rise and Fall of a Great American Family. Sterling Publishing Company, 2008. The index of the later is visible to me on google books, https://books.google.com/books?id=XAPBW7nyZEIC&pg=PA478#v=onepage&q&f=false here, and shows she is discussed on 23 pages. Neither of these are overly academic, but seem ok
Stance: keep
Cited policy: Wikipedia:Reliable sources (WP:RS)