She's said to be 'giddy' with excitement after a rumoured first date with her DWTS partner Artem Chigvintsev.And Mischa Barton was certainly in high spirits as she flaunted her beach body in a sultry photoshoot in Los Angeles on Friday.The O.C. alumni, 30, displayed a hint of cleavage in a dazzling white bikini before slipping into one-shoulder swimsuit and a romantic lace dress.