If I can be more helpful now that I have some samples of clothing & jewelry to eyeball... :-)

If the dress is the sapphire blue in the Macy's link, I think this piece of jewelry isn't strong enough in color to stand up to it. It would work better with the pink version, but still seems a little on the delicate side for such a solid dress and a solid woman. :-)

I think something that falls a little lower on the neck would work better for you. Perhaps just under the collarbones, sitting at the top of the sternum? A double strand of pearls would go very nicely with the white sandals; OTOH, a thicker gold or yellow necklace would associate itself with your hair clip.

More helpfuL? :-}