Syncing issues with multiple accounts

Got my wife an ipod touch. She did all sorts of stuff on there (downloaded songs and apps). Then she asked me to do something for her. I plugged it into my computer and screwed everything up. Somehow, her stuff dissappeared. Her contacts, her pictures, apps, songs, all gone. She was leaving for a trip and rebuilt the contacts in an hour or so. Now she wants my music off. I have no idea how to make it back to HER ipod and account as opposed to this hybred semi synced version. My concern if I log into her account on iTunes, then plug it in, she'll loose what she's put on there during her trip. Right now, she can see her music she bought, but when we try to play one of her songs, that slides by, and one of my songs start up.