I can think of two approaches this. One is that you use your computer to only activate her iPad. This is simple. Go to iTunes on your computer and signout of your account, then activate thier iPad. Stop after the registration, and before you actually sync. If you end up with iTunes signed into her account (I'm not sure if this will happen), be nice and sign it out when you are done.
This is the source of my information. It won't hurt to read it over and make your own decisions.
From Apple's Help Site: iTunes: Turning on Activation-only Mode
If you are helping a friend or family member activate their new iOS device, choose Sign out from the Store menu in iTunes before connecting the device. If you share a computer, another option is to create or login to her user account before connecting the device, as suggested in
How to use multiple iPods with one computer.
The second is to create a user account for her on your computure. It should be a plain user account, with out admin privilages. Log on to this account on the computer and use ti to set up her iPad. The seperate account will maintain a separate iTunes library.
The first method is best if you just want to get the iPad activated, and never expect to support it again.
The second is if you want to set up longer term support, say, be a place where your friend can sync, backup, and upgrade thier iPad from time to time. Make sure she understands that you, as admin of your computer, will have access to her stuff, especially if she does not sign out of her account when logging off the computer.
