You could start with just a sulfate free shampoo that will be gentler on her hair, eliminate silicones. You can still use richer products, just use a smaller amount so it doesn't weigh her hair down. Or look for lighter products if you don't want to have to worry too much about the amount you use. A lot of fine haired curlies like KCKT as a leave in/detangler and it is very light. For a co-wash, the Sauve naturals or VO5 conditioners are also very popular - others with fine hair really like the V05 clarifying conditioners as these are very light weight and don't weigh down there hair. To start the CG method, you'll want to do a final sulfate shampoo wash (just make sure the shampoo does not contain any silicones - anything that ends in -cone or -xane) to get rid of any silicones that are already in her hair. Then you can condition and style with silicone-free products.
Thanks! I started like a week ago and I pick Suave Naturals too! The leave-in is Tressemme Naturals and the gel is from Pantene, the one that is CG friendly, but I don't like it too much.

So far her hair has improved a lot, more soft and defined. My problem now is that we can't wait until her hair is dry to go out so her hair gets a little messy/frizzy on the way.