Yesterday, they had 2 sessions together. The early session, Dusty was in the kennel with the litter box and there wasn't any problem. The later session was when she was out and JD got testy.
So today, we're backing off to one session with them both in the room but Dusty in the kennel with the litter box. Maybe if we just do that often enough, they'll become accustomed enough to each other to be buddies? They don't need to be best buds--we'd settle for sharing space without getting into any fights...