As someone who would only ever pay for reduction instead of augmention, my feeling is to leave well enough alone. That being said, I would emphasize the fact that this could make a huge impact on her social consciousness, as much so as if she was overweight and lost 60 lbs. or something similar. A couple of my friends changed drastically after what you might call 'extreme makeovers.' I don't know if it was for better or for worse, but I can't argue with the theory of if you've got it, flaunt it.
Some facts to keep in mind:
--she'll need to replace them every 5-10 years
--usually, you can't breastfeed if you have kids (developmentally, this is an important nutritional factor for babies)
--they can break open if someone throws an object hard enough at her chest
--weight gain/loss can distort the shape of her boobs
--bigger breasts = more sagging later
I can't say that I would recommend going higher than a small C. With an A cup, she'd probably be better off going to a B.
