Mrs. Lahey was a recess monitor who appeared in Cabin Fever. The school banned Rowdy Riot, a energy drink which made kids hyperactive, so a kid called Leon Goodson brought a bag full of it and sold it for three dollars a can. As they knew they could get caught in the school, they went to drink it behind the school building, But Mrs. Lahey caught them. She told them to pour all their drinks out or she would report them to the principal. The boys did as they were told, but when she left, they mopped the puddles up with their socks, and let the excess drip into their mouths.
- Diary of a Wimpy Kid: Cabin Fever (First and only appearance)
- She is the first female to be seen with a unibrow.