The i3 isn't a screaming chip, but is plenty for web browsing and doing homework. The 15" screen is nice for toting around in a backpack all day - the 17" machines are a pain.
Good choice.
Also buy her a USB hard drive to back her machine up to. A 4GB or so thumb drive is also useful to transfer things back and forth with others.
If you need it portable, go with a 15" screen. If you spend most of your time in 1 place, the 17 is much better for visibility.
