Quietus and ratbastid speak the truth. I join them in the chorus urging creativity - and I know at least two of the three of us are married, so we've apparently done *something* right.
The necklace is nice, but if she really likes the dolphin one, why have something that might compete with it? Cooking her dinner is a great idea if you can, in fact, find a private place to do so. A picnic is a nice alternative to that. Check area craft shops and art stores, too. You can always find nice, unique gifts there.
My big fear is that a necklace ordered from a DVD flyer might not be the highest quality, no matter how nice it looks in the flyer. And, if so, by the time you found out, you'd be out of time and money and unable to find something really special.