I had incredibly oily hair up until my mid-30s. My hair is also very fine and very curly. I MUST use a conditioner or my curls turn all frizzy. I agree with the advice about not using harsh shampoos and to scrub the scalp well. Making the scalp too dry will increase the oil. I had excellent results with gently H&S and a leave in conditioner.

My hair was oily as a teen (not anymore). Use a shampoo for oily hair, don't use any conditioner, and only shower in the morning (also no gels, etc.) She might be sweating in her sleep at night, which would make her hair more oily. Perhaps you could try scrubbing the shampoo into her hair and washing it in the sink as a test to see if maybe she isn't scrubbing it at the scalp well.

Another poster with oily hair...just a note to make sure her pillowcase is 100% cotton. When I sleep on polyester blends, it makes it a lot worse.

Also have her put her hair up at night. The oil from hair can contribute to breakouts.

When I was that age I had horrible issues with oily hair. I would wear my hair up everyday. What I finally found worked for me was shampooing my hair twice in one shower, I would also take my shower at night and let my hair air dry completely before bed. I always used pantene smooth and sleek and it worked well for me.

Skip the organic this and that. Add a bit of baking soda to her normal shampoo once/week. Tell her to make sure she's washing her scalp and not just her hair, too.

Another option might be Head and Shoulders shampoo.