The name of this book is Indian Captive, by Lois Lenski. Most of the story takes place at the Genesee River which is now western New York. The main characters are Mary Jemison and a Seneca Indian named Turkey Feather.
Mary Jemison lived on a farm with her family in eastern Pennsylvania until April 6, 1758 when she was taken away from her family by the Seneca Indians. They took her to southern Ohio and then to the Genesee River to live with them. Mary was very scared on this long journey with the Indians. Poor Mary did not understand them and had a very hard time with them, but she soon came to understand them and made friends.
Earlier this week, the teacher sent a new book home for Grace to learn called The Birthday Car for advanced reading test purposes. Dad sat down that night to read it with Grace for the first time. After about the third page, mom spoke up and suggested that she could probably read it herself. So he started back at the beginning and asked Grace to try to read it. Of course mom was right! Grace read the entire book (first time she had seen it mind you) and struggled with maybe five words but was able to sound them out. By the second read, she new the whole book and was able to tell you the story in her own words.