How do you know that it's destroying two universes, what she's doing? Maybe she's found a safe way to come through - it's obviously different to what she's doing before. I would have thought the Doctor would have noticed if she was destroying them right under his nose. ;)

Evil Rose? I doubt it. It what way 'evil'? RTD loves Rose too much to do that... although he was perfectly happy to leave her stranded and sobbing on a beach in the parallel world. *sighs*