How to stop my wedding dress from rubbing?

I'm not sure there's much that can be done, except removing some of the embellishments under the arms or sucking it up. I think some people have previously tried body glide or anti-chafing products, so you could test those out with a little scrap of your dress fabric just to make sure it doesn't stain and try one of those?

OH! And, you could also see if the alterations person could sew a tiny bit of soft tulle/chiffon type stuff over those parts to see if that would help

Great call Stacey!! Body Glide would definitely help, and you can reapply it as needed throughout the day!

You can also have your seamstress sew a thin layer of tulle over the lace directly under your arms!