Ann Watts (McPherson?) - Please confirm how this Ann fits this family

As far as every record that I have found, Donnaidh and Ruth had only six (6) children: Nancy, Othniel, John, Daniel, Stephen, and William.
From the Birth and Death information given here, Ann would be a contemporary of Donnaidh and Ruth, not one of their children. From her location, she would not have been near Kennett Square. How does she fit?