Which aggravated me, too, to be honest. Not the first time Nightwing's been portrayed as two-timing Babs/Batgirl/Oracle and Kory/Starfire. Maybe not the worst instance, though; that'd be Nightwing Annual #2 by Marc Andreyko, in the pre-Flashpoint continuity, to explain why Barbara didn't accept his proposal in his last ongoing issue right before the one-year time-skip following Infinite Crisis.