Opal Koboi is a fictional character from the Artemis Fowl series by Eoin Colfer. After the character's introduction in in the series as a supporting antagonist, Colfer again used Koboi as the main antagonist of the fourth, sixth, and eighth books in the series, giving her the status of archenemy to Artemis Fowl II.
Opal Koboi was the main antagonist of 3 books in the Artemis Fowl series.
The statement is correct based on the information given in the excerpt. The model may have been fooled because it was looking at the total number of books instead of the books where she was the main antagonist.