Hello and welcome to healthcaremagic
Dandruff/Seborrheic dermatitis and Acne are interlinked.
I would suggest her to use an antidandruff lotion e.g 2%
ketoconazole shampoo, thrice weekly. Along with that I would suggest that she uses a coal tar+steroid+
salicylic acid in lotion form, at night for 2 weeks, to loosen up adherent crusts/scales and settle down inflammation and oozing.
Since dandruff is a recurrent problem, therefore she needs to use an antidandruff shampoo regularly, at least twice daily for maintenance of improvement.
Regarding acne, I would suggest topical
benzoyl peroxide % gel once daily for day time application.
At night she could use a topical retinoid e,g Adapalene gel over the whole affected area. Adapalene gel is comedolytic , anti-inflammatory and is useful for all grades of acne. It can also be used for maintenance of improvement.
If she has inflammatory acne, she would benefit from
oral antibiotics like either Doxycycline Or
Azithromycin.
regards