Balls are usually formal. Go with tea length to long. Don't be the one that is remembered for wearing a dress that showed way too much skin or one of the "girls" fell out. My general rule of thumb is if you could wear it to church or in front of your grandmother, then it is usually safe.
Sgt Mom
Everything becomes a little clearer, I realize what life is all about. It's hangin' on when your heart has had enough, It's giving more when you feel like giving up. ~ In My Daughter's Eyes, Martina McBride
Let's just say...you don't want to be "that girl" that everyone is talking about....you are there to represent your husband, therefore, look BEAUTIFUL. I wore a dress I wore when I was a Matron of Honor in my best friends wedding, it was pretty, long, perfect....my friend spent 3 hours curling my hair (I have a TON) and it turned out great....there were girls there that'd should have been embar***ed by their looks....just remember you ARE there to represent him, and go from there