Wait, so she's only 9 months post? That thin hair you're seeing is the relaxed hair I would think. So that's why you're seeing the difference.
I have thin (but dense hair) and now that I'm natural, it looks really thick. I think once those ends are gone it'll look better (that's if she isn't going back to a relaxer, otherwise, it will at least look the same everywhere once the rest is relaxed, thus there won't be a noticeable difference from beginning to end).
It also looks to me that her hair isn't growing out evenly. So that's also contributing to the thin look. I think that those with fine hair need a blunt cut, to look thicker. It's not something she should worry about now that it's growing out, but when she gets to her final destination. If she's doing installs, just put it back (install) and KIM. It will get better once the relaxed hair is gone, and she has a blunt cut.
IMO chlorella made my hair appear thicker (or maybe denser because more hairs grew, I guess because my hair's still look thin individually but when my hair is down it looks pretty darn thick), I also do tea rinses (nettle) so maybe that attributes.
But just doing the whole blunt cut when she gets to her final destination, and chopping off those relaxed ends will make a world of difference.