Oh right, these two are roommates. Must be a nod to their real-life counterparts.
Story goes the real-life McQueen would act like a shy schoolboy whenever he was around Dictus. Even Yutaka (Mejiro's jockey at that time) said he really liked her. Love at first sight on the racetrack, so they say (IIRC Dictus even placed 2nd in one of the Takarazuka Kinens, right after McQueen).
Later on when Dictus was retired, McQueen was also her first partner. Some horse fans also call them a husband-and-wife couple. Or that Dictus is McQueen's legal waifu.
Edit: Huh... the game also has a few scenes where umagirl McQueen acts like she has a crush on Dictus.
Updated
Tracen Academy
McQueen...?
As expected from a lady of the Mejiro family...
Hanshin Koushien Stadium
(Ref.)Starting your training regimen this early in the morning, are you...