Jennifer, I have done a few of them. They may as well be a wedding. Seriously. The only difference is that there are usually a whole lot more attendants. ALL of them in the past 14yrs have had wrist corsages though instead of bouquets.
Just do the same thing you do for weddings, try to stay away from roses, that's the "old school" I think. (but you really never know with a 15yr old!) I usually deal with the mothers, the girls are just tagging along if at all. I don't think I have any of the pictures but I will try to dig and see if I can find any, I'm terrible about getting pictures of things I never want to make again!
I will say that I think Shannon may be right on the color. As I said, I've only dealt with the mothers so everything was always pink and white except one that was lavender and white. What color is her dress?
The white mokaras and fern curls sound exactly right, maybe some wire added or bling like Shannon mentioned. That way the girl will be happy and the "old school" guests won't be horrified.