I'd actually find something vintage to wear. Or, if I couldn't find a vintage dress, I'd go with vintage jewelry - matching earrings and choker..something like this:
http://www.ultimateadornment.com/shoppingcart.php?item_id=catalog_-1254

I had found a vintage-looking A-line dress in H&M a couple months ago - unfortunaly it's not on their website. But the dress should be the easy part - it's the accessories that will make the look, shoes included. Oh, and hairstyle too.

I would go with a simple sheath dress and statement jewelry and get my hair done in a '60s style updo or blowout on Newbury Street just before the cocktail party.

Anonymous wrote:New poster here. It may be 1950s but it looks just like the Spring Dance dress that Brenda and Kelly were both wearing.

I was just going to comment that it reminds me of MY prom dress but then again, I'm sure my prom dress was inspired by 90210. Too bad my date didn't look like Dylan McKay....

I'd go with a black dress. Maybe buy some long gloves or something to glam it up a bit.