Seems that Grace Beddell, the little 11 year old girl who wrote to Lincoln and suggested he grow a beard, wrote to him again in 1864. The second letter was found in March by an archivist in Washington, D.C. The detailed story may be found here.
Her original letter ended up in the Detroit Public Library. The original second letter will remain in the National Archives in Washington. A copy of the second letter will be unveiled tomorrow at Pittsburg State University in Pittsburg, Kansas.