Here are the three dresses worn by Serena, Vanessa and Blair in 3×15 “The Sixteen Year Old Virgin”.
Serena: Contemplative and emotional in a delicate black dress with lace and cut-out detailing.
Vanessa: Striking a powerful pose in an artsy dress and subtle fishnets stockings.
Blair: Distraught as usual (what did Chuck do NOW?), she looks fiery under the ice of her eyes in her strapless black and red floral dress.