My daughter had her prom makeup done at Simonsons last May and both gals working there that morning were probably around your age. Everyone commented on her makeup because it was not overdone but definitely formal. It complimented the dress and hair perfectly. I was totally impressed. I wish I could remember the gals name but I was pretty nervous that morning :).
So, I would recommend them but the downside is... do you really want to get your product there? The product you use can make a huge difference. We bought the lip gloss she used so my daughter could re-apply and it was $25!
Back when I was working, I was very into Estee Lauder but since I'm home with kids now and shouldn't be spending that kind of money, I have really enjoyed Mary Kay. There foundation rivals the Estee Lauder brand and it is $21 cheaper! The other nice thing about Mary Kay is they provide ALOT of education on application. I thought I knew the best way to do my makeup, colors to choose etc. (I've always been a makeup girl) but my girlfriend had a show and I learned so much. I always thought is was for old ladies but I guess I am one now! I think they teach a very "polished" look.
Good luck!