let me guess, your girl probably has an A-B cup, give or take. It's probably not as bad as you're explaining but I would need a pic to at least guage the sluttiness. I think it would probably look decent, like a red carpet gown.
Also, understand that this season's prom dresses are a lot more provocative than before.
But here's an example of what I was talking about. It's clean looking, not slutty.
And FYI, don't be such a pessimist. If she's proud of her body, then let her be. Most white girls fall off after high school so enjoy it. :lol: