How do I set up an iOS device on new account without losing app data?

I apologize that this thread is not directly iPhone related, but it needed to be posted in an iOS forum and iPhone seemed to be the one with the most traffic.

My problem is that my sister's iPod has been on my iTunes account for a while now, but new features are making this more difficult. We were able to work around FaceTime, but she cannot have her own GameCenter account and iCloud will not be friendly to people sharing iTunes ID's from what i hear.

So obviously I want to set up her iPod on an entirely new iTunes account. My problem is her apps. She's purchased only about $30 worth of apps, so I would not mind paying a one time $30 "fee" to rebuy everything on a new account (my understanding is that apps bought on one account can't be used on another).

My problem is the app data. Lets take her Fruit Ninja high scores for example. Is there anyway to transfer it over? The only thing I can think to do is backup the iPod before changing account, change accounts and rebuy apps, then restore the iPod from the backup on the new account. I don't know if that would work though. Is there anyway to do what I wanna do, or would she have to start from scratch on each app?