I don't like that question because it presumes that women wear jewelry as mean of disguise.
Far from it! Jewelry is one of the highest and most personal forms of self-expression. It reflects who we really think we are. So there is no jewelry that can apologise for your existence. There is only jewelry that is designed to celebrate the joy of your being, no matter the size of your breasts (or how many you have)!
A better question might be what necklace is right for the clothes you have on at the moment? You wear different jewelry based on a variety of parameters. Are you wearing a turtle neck, are you wearing a bustier? Are you dressing for the office, digging a ditch or a cocktail party? What are you doing? Are you standing, walking around/active, or sitting at a desk or on a stage?
My philosophy is that with the right jewelry, it doesn't matter what's underneath; you could be naked. Because if you are wearing something that makes your heart sing, you will be beautiful.
