Fair enough, but seeing as the iPhone gets slated for it's battery life and her old one had more battery-draining features enabled (and was 2 years old) then I would have expected a brand new phone to last at least as long.
Is this the cell standby reporting bug? I read about it but as I understand Samsung themselves haven't fixed it yet? The phone itself is fully updated as far as I know, guessing it will only get fixed through official channels when the JB update comes out?
Try and update via Kies to be sure it is fully updated. Some updates do not work over the air.