Last night, Blake Lively celebrated the premiere of her Gossip Girl co-star Chace Crawford’s new film, “Twelve.” But while we normally love Lively — and her mind-bogglingly fabulous cleavage — we’re a little disappointed in this dress. From Chanel’s 2011 Cruise collection, the dress features an open back — which is great — and a flower-patterned lace midsection, which is not so great.