Thanks everyone! To those worried about the boob exposure in dress 1--I have to admit, I don't mind bringing attention to my chest (as long as I don't think it looks squashed, unattractive, etc.). I spent many, many years loathing my bust size, and now I just embrace it without apology, and don't mind a bit of exposure. But no worries--I would never, EVER wear something like that to work! In fact, I wouldn't wear either of these dresses to work--these are for non-work occasions only.
I am going to call Nordstrom customer service and see if I have more luck there than I did when I called my local store. The local store did check all of the inventory, but maybe main customer service has some other options? I fear that the dress from the Nordstrom site is actually a couple of years old, based on some research I did, and that it was simply reissued by Nanette Lepore at her boutiques this year. But we'll see.
At the very least, it seems most people agree that the dresses are different enough that the similar color doesn't make them so similar that I couldn't keep both. Now to decide if I want to keep the new one or not. Thanks again!