Why does Huck tell Mary Jane to leave before breakfast? What is he concerned about?

Huck makes Mary Jane leave the house and stay with a friend across the river. Before she leaves, he writes down where the money is located so she will be able to find it later on. Huck is afraid that if Mary Jane stays at the house, her face will give away Huck's indiscretion. Huck tells her sisters that she is across the river trying to stir up interest in buying the house. After telling this part of the story to the reader, Huck remarks that he has never forgotten Mary Jane and still thinks she is one of the most beautiful girls he has ever met.