A new photo of Sissi has appeared lately on tumblr (antique-royals.tumblr
). On it we can see Empress Sissi, her sister, Helene aka "Nené" and a lady in waiting (Hunyady Windischgratz). ca. 1860.
But lately I found that it is just a detail of a larger picture...Taken from: sweetlydreamingofthepast.blogspot.com