Can’t sew bra cups into wedding dress?

Hi all,
So let me start by saying I’m a 32G bra size. My dress is gorgeous but has an open back underneath a sheer layer of beading. Everyone at the bridal salon told me I’d be able to have cups sewn in and it would be fine. At my first fitting, my dress maker told me she wouldn’t sew bra cups into my dress because it wouldn’t give me any support. She instead told me to go find a low back bustier. So I found the lowest back bustier in my size/sister size (made by Le Mystere) and go to my second fitting. She tells me it still isn’t low enough now in the cups/armpit area. So I immediately start to cry and ask her what I can do. She said that I need to try one of the adhesive backless bras (specifically, Nordstrom). I told her that I’ve previously tried these kinds of bras but they don’t offer enough support for me. She told me how I must’ve just been putting them on wrong. Sigh. So I order one. Try it multiple ways and surprise, surprise. It doesn’t hold me up. I’m dreading my third fitting in a few weeks because I don’t know what could possibly be done. She insisted I couldn’t have cups sewn into my dress. Anyone have any ideas? Thanks!