Hi! I'm a lurker. I don't think I ever posted, and when I do, it's not even about me.

This isn't exactly CG or no 'poo or curly relevant, but if anyone could help, I figured it'd be some of you guys. So don't shoot me for being too horribly off topic. :/
I'm a live in nanny for a couple of friends, and one of their daughters is 12. She has what I suspect wants to be loose wavy hair, 2a. Individual strands are extremely, extremely thin, but there's a lot of them. It frizzes. It's a mess in general, and seriously, it
mats. I'm a veterinary technician. It gets worse after a day than many mats I've seen in cat and dog coats.
Her mom purchased a Just For Me! conditioner for her, somewhere, which she's been using periodically. Primarily as a means to facilitate combing out knots without bursting into tears. Any conditioner, she claims, makes the problem worse.
My hair is similar, 2c or so. Very, very coarse. I used to be no 'poo due to having incredibly hard water which destroyed my hair, but moving back into soft water means that I can use it again. I use Trader Joe's Nourish stuff on my hair 1-2 times a week, only shampoo my scalp, use conditioner to detangle with my fingers in the shower, and a leave-in conditioner on top of that. Granted, that's when I'm leaving my hair up all the time. If it's staying down, it's more 2-4 times a week. I never, ever touch it with a brush or a comb. I'm not sure the same routine would work for her, because she tends to wear it down.
I'm in the middle of a marathon brushing session, trying to get all her hair untangled, which prompted me to come here. I feel more like a whiner, so I guess my main question is more a plea for help, any kind of help.

Does anyone have any ideas about what's going on (too much moisture? not enough? bad rinsing?), what could make things easier, how to avoid the matting? I desperately want to break her of the sleeping on it when it's wet habit. And what would you use to brush or comb? Her mom thinks a paddle brush is Win, and that kind of makes me cry.
Thanks for any ideas or help at all.