The same thing happened to my daughter, her skin was worse just before her periods. Anti biotics didn't help, the GP referred her to a dermatologist, who put her on Retinol Cream and another type of antibiotic, every day. Eventually now, after about six months, her skin is much much better, she is now taking the anti biotics every three days instead of every day, and is going to stop completely. So fingers crossed it doesn't come back. Some people are more unlucky than others in getting rid of the acne. And her confidence was at an all time low, I felt so sorry for her. So it will not go quickly unfortunately, but take a photo of her when her skin is really bad, to show the dermatologist, and the best of luck. Hope she enjoys her prom, maybe her skin will be better that day. It does come and go. My daughter used Laura Mercieer makeup when her skin was bad, it might be worth investing in some foundation so she feels good at the prom. She was 'made up' at Laura Mercier in a department store, the coverage over the spots was fantastic, and then bought the foundation online.