Yep you play as Edea (or CAN play as Edea) until just after you get kicked off Lunatic Pandora. Then she finds out she's not a sorceress anymore. After that, you go the the ship and start the space sequence. After that, it's edea no more.
I woulda liked to have a chance to play as seifer for longer, he was cool. Like it woulda been good if you could have defeted him later in the game and then got him to see sense and join your party. That would have been class.