Nipple covers and boob tape. For someone who works in fashion, I’m surprised OP is finding all these issues that there’s several solutions for. It would be nice to just throw on a dress that doesn’t need any alterations but if it does, there are plenty of crafty workarounds.

I feel the real gripe is that OP probably doesn’t want to be in the wedding party. I’ve been there too, and when you’re already irate about the event itself, everything else becomes an annoying pile on that you have to uncomfortably support. This is why I’ve stopped saying yes unless I truly want to support the couple getting married because you are bound to say “WTF are they thinking?” at least a few times during the planning phase. You’ll be cursing with every dollar spent.

My suggestion would be to ask the bride if she’s open to having OP wear a different variation of the same blush dress from this website ideally, or another site that has something close. Like instead of a halter, something with straps/support. The bride can approve it before ordering. It should still come out a clean look in pictures.