Take her to a dermatologist. We did this when my daughter was 11 and no skin problems. We did it as a proactive approach to what may happen because we had seen many teens with horrid acne and she was terrified it could be her next.
She started out using Clinique Acne wash and the gel moisturizer. The Dr. did give us an RX creme for breakouts. Beware though, many insurances do not cover it and I have paid as much as $300 for 1 tube of Epi-Duo and $200 for Duac and Differen. Both work well if you have an issue but they willl stain clothing and sheets. It is worth the $ to go to a good, highly recmmended Dr. My daughter did not need antibiotics, etc. She just got a couple of cremes to help when she had a breakout, not for continued daily use.
My daughter's worst time (which was never that bad) was when she was around 12 and started her period.
Clinique is a great product with several options to help you. Many Dr's recommend it. It is a money back guarantee as well. I have used it since I was about 11 and I am now 49 and pass for early to mid 30's.
Other products Dr's recommend is Purpose Soap and Cetaphil.
Next, get into a routine that you do not break ever. This consists of washing, moisturizing, etc EVERY morning and EVERY night. Use sunscreen and drink a lot of water.Be faithful with your routine and when she is 49 she won't look it either.
Good luck