According to her article in thepeerage, she was Maid of Honor to Queen Adelaide and, as a result of her marriage to Henry Richard Charles Wellesley, 1st Earl Cowley, became Baroness in 1847 and Countess in 1857.
From Paul Frecker; image lightened to bring out skirt details and sepia tone removed by gogm (and re-added to the border only with Photoshop).
Lady Olivia's coiffure is plainly outdated. Her neckline is hard to resolve, but the most visible neckline is a square neckline that would be in fashion a decade later. Her bodice appears to have ruched panels similar to revers a century earlier.
Keywords: 1861, Silvy, Olivia Cecilia FitzGerald de Ros, FitzGerald de Ros family, Wellesley family, Countess, Lady-in-Waiting, Queen Adelaide, British, hurluberlu coiffure, high neckline, partlet, square neckline, ruching, revers, stomacher, long pagoda sleeves, crinoline