Lily lived in Quaker Valley, Oregon, and was the wife of the local sheriff. One day, the deputy attacked her and transformed her into a Nachzehrer. Lily passed the curse on to her children, but her husband refused to join, so Lily killed him.
Dean managed to kill Donelly, thus reverting Lily and her children back into humans. Lily immediately showed remorse for her actions. Sam and Dean then drove her back to reunite with her family.