to seperate school account or keep together her itunes account
Even using the same Apple ID there is no requirement to load the same apps onto different devices.

I have an iPad and iPhone with my AppleID and completely separate sets of apps on them.

Assuming you're using iCloud, it might help to have the same email address accessible on both.

You can download apps with a different account to the one setup on the device for iCloud as well, which is another consideration.

You could create different iTunes accounts to distinguish between school and home purchases, and still use the same iCloud account for email, calendars, etc.

It depends on your ultimate requirements as to which media you want accessible on which machine - sharing music, photos, email, calendars, apps, books, etc.

Generally, it's easiest to share the same iCloud account, and App store accounts, but you can split them out as required.