Wow, this child is so gifted! This is exactly what my DD5 was doing at this age (my daughters reading was a bit more extentive and her voice was clearer, but along the same lines), it's amazing to see another child doing the same thing. It's not because of the sign language, it may be she has a photographic memory like my daughter, so they memorize everything put in front of them and have an amazing understanding of phonics, math, and just a endless interest for knowledge.