In S01E01 of Justice League Unlimited, Green Lantern, John Stewart, is wounded while on a mission with three other members - Green Arrow, Captain Atom, and Supergirl (Kara Zor-El). Believing Stewart to be unconscious, Kara interrupts the bickering Atom & Arrow to say that she is taking action since they won't. As she goes to leave, Stewart calls out and tells her she needs a plan first. When he calls her, however, he says "Shayera" instead of "Kara".
Is this an error on the part of the writers?