Most women envy your body type, but it's probably hard for you to find dresses that make you look like the emerging young woman you are, rather than an adolescent. Select a dress that will accentuate your waistline and highlight all of your best features. Dresses with full skirts, pleats or layers will give you volume in the right places, while creating a more aesthetically pleasing silhouette.
A large bust requires a supportive dress, so look for one that has straps that will allow you to wear a bra. You may even try a one-shoulder dress that will give you support up top but also add an element of style with the right bra. Avoid spaghetti straps and the temptation to hide your bust with a high neckline. You can achieve a good fit with the right amount of sexy by choosing the right dress. You can try a dress that emphasizes detailing with an empire waist or an A-line cut that minimizes the top while accentuating the bottom.
Choose a dress that distracts and diverts attention away from your mid-section. You can accomplish this with an empire-line neck and/or waist. Play up your assets. If you have nice arms and legs, you should consider a short dress with spaghetti straps.
Dresses that are loose and unfitted in the bottom half will camouflage the problem area. A-line dresses easily accomplish this goal. Highlight your shoulders and arms with a strapless or one-shoulder formal evening gown. If you want that sleek look...a chic floor length will always stream the lines.
There are a couple of things a petite woman can do to appear taller. Most obviously, wear heels. If prom will be the first time you wear them, just make sure to practice, so you feel confident walking around. A dress with an a symmetrical hemline will also make you look taller. Avoid long, full dresses, as these tend to swallow your body. And...if you do wear those heels...be sure to wear a knock-out pair of platform stilettos and allow the dress to cover the heel. This will give the illusion of a taller silhouette.