Help for daughter's very dry flaky scalp? (She is 11)

I have slathered her scalp in baby oil, creamy baby oil, coconut oil and even used a scalp treatment from deva curl that she said stung. She has very curly hair, so a big part of the problem is that she has it up a lot for school because it is more manageable in a ponytail. But this creates a breeding ground for dandruff, buildup ect. I'm at a loss. She showers every other day since it is winter. I shampoo her hair so I can make sure I'm getting in there better than she can and it is still so flaky. It used to just stay close to her scalp and no one could see it, but now it's sitting all over where everyone can see it. Her hair is coming out so much because of it. She is extremely healthy, eats tons of vegetables, fruit, protein so I don't think it has anything to do with her health. I'm just at a loss. Do I take her to the pediatrician? Dermatologist? Not sure what to do for her anymore, I feel like I've tried it all.