if she's not going to run any modeling programs or play games, a laptop would probably be most convenient. They do break more easily, and are slower, but they're also easier to take into the shop =p Find out the return and warranty policies and buy based on those, they are pretty much the only difference in pre-built laptops. They all use the same generic sub-standard and sometimes refurbished parts. How fast will they fix dead pixels? Can they offer a replacement while they mail it back to the factory for repairs? They will *not* be able to fix anything hardware on a laptop at a local store.
As far as peripherals go, as long as you get USB2.0 (standard now), you can buy a hub and plug everything into that. USB keyboard, mouse, printer, even network card if needed. Won't have to use the flimsy built-in keyboard.
Whichever way you go, make *sure* you find out how fast they can fix it. up to 20% of these things can ship with dead pixels out of the box, depending on the brand. They tried to charge me 700$ for a broken power input at Best Buy less than 2 weeks after I bought it, and I've had to fix all kinds of problems.
You'll probably end up having to buy more RAM as well, prebuilts generally come with only 256, sometimes shared with video ram down to ~200, nowhere near enough to run even basic OS functions and office programs.
http://www.crucial.com will tell you exactly what kind of ram slots you particular model/brand of laptop can use; total slots, free slots, and default amount of ram included.
I'd recommend adding 512 to a 256, especially if it shares ram with an onboard video card, if slots allow. otherwise you might end up tossing the 256 stick if there is only one slot (or ebay it).