Sounds as though you're giving her good advice. I would add: throw away that flat iron. It's probably the single most damaging thing she's doing to her hair and is probably the major culprit in her split ends and stalled growth (I bet her hair is growing, but breaking off at the ends as fast as it can grow out at the roots).
I'd probably start by clarifying and then using a good non-coney conditioner. I say non-coney because if she's going to start oiling, she doesn't want a layer of cones keeping the oil from penetrating her hair. If she finds her ends are tangly, she could try a tiny bit of pure shea butter just on the ends. I have a small amount of residual heat damage on my ends and I find that shea helps them a lot when they want to become grabby.
You don't say anything about her texture, but if her hair is frizzy that might be an indicator that she's wurly or curly, so try air drying to see what comes out. If she has to use heat, a blowdryer on cool -- cool enough to keep your fingers in the airstream -- is reasonably hair-friendly in my experience, but will still cause more frizz than air drying with no interference.
Dandruff shampoo -- does she actually have real dandruff or is her scalp just flaky from too much detergent? I find that soap-based shampoo bars are much gentler on my scalp and make it much less flaky than any shampoo I ever tried.
Very tight ponytails are probably not a good idea. Is she at least using safe, metal-free elastics? Perhaps she could consider replacing them with a Flexi in the right size? The website has sizing information that should help her decide what she needs for a ponytail.
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