Shannon, I haven't read all of the responses and I'm not sure you can stand one more opinion but -- here goes any ways.
I like the dress and color on you! And how kind of you to want to wear it to your friend's wedding, you are so thoughtful!
I believe you could have the dress taken up/altered at the top straps so the distance from neck to bust is shorter. The whole dress is lifted a little, maybe an inch or so. I have this problem all the time. I am petite (5.3-1/2) and further more am very short from collar bone to top of bust. Armholes are frequently way too big on me for this reason. I have had sleeveless dress altered by taking some fabric in at the top seams.
Then it would be easy to find a bra that will work underneath the dress. Plus, the dress would have a little more coverage around the armholes for modesty.
You have nice shoulders -- no need to hide them with a jacket once you've got the armhole issue tackled.