Tower Coordinator described a potential conflict when opposite direction departure traffic did not turn as expected; the reporter indicating the slow turn looked like an 'enroute' type turn.

Narrative

A B777 had been waiting for approximately 30 minutes to depart opposite direction to the arrival flow - east wind. Before departing; the B777 was issued initial heading and Departure Control frequency; which was read back correctly. Training was in progress on Local Control. The instructor prompted the developmental correctly as they had not seen this operation previously. On the upwind with a CRJ7 at the final approach fix inbound; the B777 was slow to begin their turn to the northwest. This was unexpected. The developmental told the aircraft to begin their turn. The Departure Sector Coordinator called worried the aircraft was not turning; I advised they were now in the turn. I then called the Arrival Sector and advised that the B777 was in fact in the turn. We ended up with what appeared to be 5 1/2 miles looking from point of turn out versus the CRJ7's arrival track. This should never have been this close. Recommendation; have pilots fly the airplane in a manner conducive to the environment they are operating in. This looked like an enroute turn.