Hello,
Welcome to healthcare magic.
Acne and dandruff could co- exist in a teenager as both are realted to the maturation of the sebaceous glands.( oil producing glands which are concentrated on the scalp and face). However, dandruff is not a cause of acne.
For her acne, let her wash her face with a pH balanced face wash, preferably a one containing 1-2%
salicylic acid. You may apply a gel containing
clindamycin 1% in the morning over pimples and
Benzoyl peroxide 2.5% gel at night over pimple prone areas. Get these prescribed by your doctor.
For her dandruff, use a shampoo containing
Ketoconazole 2% and ZPTO 1% thrice a week for a month. After that continue using one a week at least for maintaining the improvement.
Avoid creams on her face. Avoid too much oil on your scalp. Diet is important. Avoid milk and milk products like cheese, chocolates, sweets, sugary foods and drinks. Eat a lot of fruits rich in
vitamin A.
Hope this helped.
Take care.