Get her to see a dermatologist.
My experience (had really heavy acne all through my teenage years):
- All creams etc that you find in a drugstore/supermarket are worthless. Frequently washing the skin to keep if from getting oily, and a good diet help a little, but not much.
- Vitamin A Acid treatments help, but only as long as you use it, and it's quite aggessive on the skin.
- Accutane pills (called roaccutane in some markets) is by far the best way to get rid of Acne for good. Took it for six months five years ago, and havent had a single problem with acne ever since.
Some caveats: She absolutely cant get pregnant while taking it (it harms embryos), it may have side effects like dry lips or skin while taking it, and you need to have your blood levels checked regularly while taking it. And check if her insurance covers it, since it's quite pricey (in Europe: about 1500 dollars for the usual six-month treatment). So not the easiest way, but very effective, and I'm very glad I had a dermatologist who recommended it.