Is she the author of books such as "Rambles in Cairo" ?
The library of congress gives "Mrs. R. L. Devonshire", with a birthdate of 1864.
Devonshire, R. L., Mrs., b. 1864: Rambles in Cairo / by Mrs. R.L. Devonshire. (Cairo, [Egypt] : Sphinx Printing Press, 1917)
Devonshire, R. L., Mrs., b. 1864: Some Cairo mosques, and their founders, by Mrs. R. L. Devonshire. (London, Constable & company, limited, 1921)