I also have curly hair and didn't really learn how to care for it until I was about 20... basically in your situation the only time you should be brushing her hair is if you are styling it or after a bath. When her hair is wet, run a large tooth comb through it - that's it. You might want to get some large clips and put her hair up before bedtime so it isn't so tangled in the morning. She should be able to shake her hair out in the morning and that is all.
You don't want to use too much detangler or leave-in conditioner because it isn't that great for her hair, but try a couple brands to see what your like and what works best for her. After a shower I use Anti-friz stuff called "frizz Ease" that works great (it is the only product that I need). They don't carry it at Sally's anymore but you can get it at WalMart.