Family portraits

Ducky was only in Hesse-Darmstadt for a few years and the impression she left was not overly positive, so I would not think she would figure greatly in any book, catologue, or exhibit related to the Hesse-Darmstadt family.  

QV had a portrait of Ducky commissioned in 1896 by von Angeli.

Princess Alice by Winterhalter

Is that a bridesmaid's dress for Vicky's wedding ? 

It looks like it the bridesmaid's dress but not unless the dress was reused. The description about the painting describes her as wearing 'the dress in which she appeared aat her first drawing room' in May 1859. The portrait later hung in Princess Beatrice's sitting-room at Buckingham Palace before being transferred to Windsor in 1915. R.J. Lane made a lithograph of the portrait (found at the National Portrait Gallery). QV wrote that Alice 'looked so nice in tulle over white silk, trimmed with pink roses & lilies of the valley, a train of white moire, trimmed the same, & a wreath, faethers & small tulle veil on her head.'