Posted to the Alexander Palace Time Machine Discussion Forum by Grand Princess Shandroise on 5 June 2012.
This is probably a costume party costume. I have no idea who Alexandra is mimicking or what role she may be playing. Her dress has almost no bustle at a time of big bustles and it has a waist band and I cannot tell if it has a vee waistline or not and what neckline it has - square, trapezoidal, or sweetheart. She also wears a braided bun à la Sisi with a small fleur-de-lys in front.