Save that dress for a date to Vegas with your BF.
You're going to a wedding.
If it's a church wedding, if you wouldn't wear that to a church, you wouldn't wear that to a wedding.
Since people don't marry in church anymore, it's still something you wouldn't wear to a wedding!
It's the bride's day, attention goes FOR THE BRIDE!
The ONLY place I could think of, where you could also wear that dress: A batchelor's party for the ex, and you're the girl who pops out of the cake!