I see one issue off the bat. You need to transfer her purchases into the iTunes library before you update, restore - or do anything else. Don't let iTunes erase the iPad.
After you do these steps - then follow the steps listed below. Read them first and make sure you understand the process. If you follow these steps - it should work.
Do the steps in this order - do not connect the iPad until you turn off auto sync as described below.
I setup an account on my pc for her
I signon to the new accont and start iTunes.
I signon to apple using her apple id.
I authorize my pc for her iPad
The following was copied from this thread. This is essentially what you want to accomplish.
https://discussions.apple.com/thread/2431472
1) Without connecting your iPad to your laptop, start iTunes. Click on Edit. Click on Preferences. Click on Devices. Check the box next to "Prevent your iPod etc. from automatically syncing." Click OK.
2) Now connect your iPad to your laptop and start iTunes.
3) When iTunes starts, right click on your iPad under Devices in the left column. Select Transfer purchases etc.
4) After it finishes transferring all your apps to your new laptop, right click on your iPad and select Backup your iPad.
5) After it finishes backing up your iPad, right click on your iPad and select Restore etc.
6) After it finishes restoring, left click on your iPad , then click on the Apps tab on top, and check the box next to Sync Apps, then click on Apply below.
If everything on your iPad looks good after the sync, go back and click on Edit / Preferences / Devices and UN-check the box next to Prevent your iPod etc. The only other thing you may want to check is if your contacts, bookmarks, etc. are syncing correctly now. If not, go to the Info tab after connecting and make sure you indicate which features you want to sync with what sources.