There are, I believe, comments on Susie's death in the MT-Howells
Letters. Howells' daughter Winnie died at about the same age as Susie
(although several years earlier). In one letter to Twain, Howells quotes
Emily Dickinson (the poem about the bustle in the house the morning after
death) as a source of solace. Sorry I can't give specific cites--books
are at home.
Kansas State University