I bought my father an iPad and set it up with my iTunes account. Bought a few apps and loaded them also with my account. There were a few problems.
Before I gave it to him, I set up an iTunes account for him, switched the iPad to his account.
Before he synced it there were updates for some of the apps, he had to switch back to my account to get the updates for the apps I bought , then switch back to his account for the ones he had bought.
When he synced it with his iTunes on his computer he got a message that you can only have it synced with one iTunes account. It deleted the apps I bought and put on with my account. I contacted Apple customer support and begged them to take pity on two senior citizens that were first time iTunes users and fix it for me, they did and said it was a one time thing.
It would be much less confusing to do what the previous poster suggested. Set up an account for her, use a gift card and your address. You can load everything you want while at your home, just don't sync it with your iTunes account. Her parents can change the payment method later, or keep reloading gift cards.