How often is she going to be lugging it around? If the answer is more than once in a great while I would have to strongly suggest going with a laptop that weighs no more than 4.5 to 5lbs. I'm starting to look at replacements for my Dell 700m (12.4" 4.2lbs) and while I am thinking about a slightly larger screen size, I don't want to add much weight. I'm not pulling the trigger for a few months at least, but if I had to buy something now I would consider this:

http://explore.toshiba.com/laptops/satellite/U300

Hard drive sizes are usually not that critical (just about all are at least 160GB these days which is sufficient for just about anyone who isn't making HD movies), nor can most people notice the difference between various processors (really any dual core processor is fine.) But a laptop that's lightweight is a different story. Just make sure it's got 2GB Ram and she should be good to go.