Hi melissa,
I just thought I would mention that if your daughter doesn't have great success with the Neutragena kit there is an excellent acne system which can be ordered online called Exposed Acne Treatment System (www.exposedskincare.com).
After YEARS of trying everything (I'm 35 and have been dealing with acne since I was 11), this kit has made a huge difference. It's great for all ages. I found it in an unbiased acne skincare review which included many of the most well known acne treatment regimens (Proactive, Murad, etc.) Exposed was rated highest, and each of the judges had seen improvement from it - that's why I gave it a shot. I've used it for over a year now.
Other than that, I would say put your "mommy detective hat" away. They hate when we do too much of that, you know? For many people acne is just part of life at one stage or another and it's probably not the mineral makeup causing the blemishes. If you order her the kit and tell her to ease into it at first (don't use too much in the beginning and let her skin adjust to it) and just say you heard it was good - maybe she'll give it a try. With any skin care regimen, you have to give it time (months) to make a change to the complection. There are not usually immediate results. The kit she's using now may be enough to do the trick for her if she sticks with it.