Hi Cyan45,
whilst I'm not an expert on these things I am a small busted gal. I think this could work, if you wanted to 'fill' it a little more, you could use chicken fillets.
I suppose the one thing you would have to do is to try it on and see just how much you 'fill' the cup of the dress. Usually frills etc help to make make you look bigger up the top, so it is worth giving it is a go. At least trying it on.
But as I said, I am no expert, Angie may disagree with me totally.