Derelict
Sandra wasn't mentally disabled or particularly stupid. She was, however, incompetent and lazy. Sandra was supposed to pay the bills for the department. Doing her job was a bit too much effort for her. So Sandra merely did nothing and seemed to get away with it.
So Sandra merely did nothing and seemed to get away with it. Sandra was supposed to pay the bills for the department. Sandra wasn't mentally disabled or particularly stupid. Doing her job was a bit too much effort for her. She was, however, incompetent and lazy.