I would choose no necklace at all, and dangly earrings of a variety of possible types: either pistachio (sp?) or peacock Tahitians, maybe just WSSP (though this is my least favorite of those I'm listing) or pink sapphires or citrine (non-pearls, I know). But whatever, I would choose monochromatic and a color that matches one in the dress. Maybe I'm boring, but that's what I'd choose.
I love her current earrings; however, I think something else would look better with her dress, especially if you removed her current necklace.