oh great, shogmaster. :/
i think the ibook is a good choice. if you don't live in california, buy from the apple store on edu discount (this should be the same price your girlfriend's school bookstore will offer and ~10% off). if you do live in california, you may be able to save some money by buying on the edu discount but you're more likely to get around the same price through one of the mail order houses (macmall, macwarehouse, etc. etc. starting reading macintouch, macnn, etc. and find the price engine that lists out shipped prices and current incentive - ok, so the way mac pricing works is apple has very strict price controls, but the dealers are allowed to offer incentives like free hardware or whatever - so that's how you're going to find the best deal).
anyways, the ibook is a decent package for editing because the software end of it is so clean. your gf will probably do some training on final cut, etc. as part of her schoolwork because it's just so accessible. as far as the hardware trimmings, you will end up spending a little more, because you'll need more (and possible faster) storage as well as some memory to keep things rolling. however, i wouldn't recommend a wintel laptop because you're not going to find an equally portable machine that's so suited to her application and as clean software-wise for the same price (if you could spend a little more... maybe.)
oh, video chipset will matter somewhat even for editing because the os x display engine uses the opengl pipeline even for flat 2d renders (since it's all vector). a 9200 will probably be more than competent, though.