I never thought she was in morning in that portrait since she s wearing blue, not black.
And...curious tip: that portrait was given to his brother in law, the duke of Alba, her teenager love , in 1862.
here we go...
Munn, Tiaras, A History of Splendour p 54 plate 37
"(opposite) Empress Eugénie , painted by Franz xaver Winterhalter in 1862. By the time this touching portrait was painted, the Empress had endured much personal suffering and sorrow, and the artist made no attempt to disguise it. Here she is wearing a Spartan diadem and veil, obvirious signs of mourning for her sister, the Duchess of Alba. (THE DUCHESS OF ALBA, PALACIO DE LIRIA, MADRID)"
in this photo it's black, not blue and with this very restricted jewesl (in contast to her other formal paintings (white, airy dresses - also Winterhalter)) and the veil it make sense. and as Munn correct some errors which occoured before (Field, Menkes) I think that's true what is written.