I think I read this in the 4th grade (I was born in 1979). This girl was really unhappy at home, so she took a boat and rowed away to an island. On the island she learned to fend for herself. She made a cozy home either in a kind of dug out, or a hollowed out tree. She survives the winter, and eventually returns home feeling much better about herself because she has lost weight and is independent.