The Celtics employee with whom Ime Udoka had an affair helped make all his travel arrangements ... and that job sometimes included organizing travel for his fiancee, Nia Long.
Sources connected to the couple and the NBA franchise tell TMZ ... one of the staffer's duties included planning Udoka's team-related travel, and we're told she was also involved in booking travel for Nia to come to Boston or to road games.
Perhaps most upsetting for Nia is that the employee had a hand in Nia's arrangements to move to Boston permanently, according to our sources.