Who cares really? All that matters is she's ok. As long as she is not telling other people that they can cure ADHD by purely eating & sleeping better, I don't see a reason to complain.

actually a lot of people age out of ADHD (according to dsm and actually studies)

Interestingly enough, some foods actually do help manage ADHD symptoms, so be careful as this might be placebo / nocebo effect sure. But it might just be a combination or Iron, magnesium, B6, B12, omega fatty acids and more proteins in the diet and some part (self CBT). While ADHD is genetic, it does not mean medication is the only right option (it is firstline)!