Meh - I don't know about that. Their being friends might actually explain just why her betrayal hurt both sides so much. I mean, Batman has been betrayed multiple times in his life, and generally, he rolls with the punches. HE'S done some betraying, himself - looking at what Ra's al Ghul did to the JLA using his methods - but he was ultimately forgiven for it. He doesn't LIKE being betrayed, of course - who does? - but he generally manages to put his resulting anger and suspicion on the backburner after a reasonably short period of time. But as best I've gathered (and admittedly, I haven't read all the issues involved here, but still), he was really, really hurt and angry by what Zatanna did to him. He didn't let her forget it for quite a long time. A long-lasting personal connection could explain that - when an old friend betrays you, it really hurts.