In the story Monaghan tells about the War, this "girl" accompanies Bayard Sartoris to a "dive" in London while he is in England training as an aviator. She becomes the occasion for one of Bayard's barroom fights when an Australian captain "just tries to speak to" her (385).
He is mentioned by Monaghan, who says that during the War Young Bayard "knocked two teeth" out of this "Australian captain" in a fight over a girl in a "London joint" (385). This officer's role closely resembles that of the unnamed Australian officer Bayard tells Rafe MacCallum about much earlier in the novel, but that officer was a major, and the nightclub was in Leicester.
This very peripheral character figures in one of Monaghan's anecdotes about his experiences with Bayard Sartoris in World War I as the "A.P.M." whose whistle Comyn took and used to start a melee in an Amiens night club called the Cloche-Clos (387). The Provost Marshals ran the army's military police.
