Get rid of that flab with these exercises!
The+Only+Exercise+You+Need+to+Look+Amazing+in+Any+Bridesmaid+Dress - Cosmopolitan.com
Strapless dresses tend to accentuate armpit flab. Target the pesky area with a front raise-lateral raise combo.
Push-ups with side plank extensions build chest strength to help your girls hold themselves up (or do the best they can under the circumstances).