why doesn't mattie just get a job and place of her own?

Mattie's father was Zeena's cousin. He had left the hills and traveled to Connecticut, but he died too young to make his fortune. His wife died soon after, leaving Mattie to fend for herself. She had no real skills, and the difficulties of working for a living disagreed with her health. When Zeena's doctor recommended that Zeena find a housekeeper, the family arranged to have Mattie stay at the Frome farm.