I spent a lot of time on a laptop purchase last summer, so I know what it's like to be in that position. My needs were fairly different, however -- I ended up spending about $1600 on my laptop because I like to game in my free time.
Some quick-hit advice (I had a longer post but it got DELETED because of the darn timed-auto-logoff functions of these forums).
1. Even a user with "basic" needs will appreciate a computer with fast specs. Weaker specs can bog you down even if you're just web browsing or word processing. The processor speed and the RAM is most important for this, though you never need more than 6-8 GB of RAM.
From what I recall getting a PC with closer to 6-8 Gigs of RAM doesn't up the cost that much, and there were some laptops with and i5 or i7 that were reasonably affordable.
2. Consider getting a laptop with the operating system installed on a Solid State Drive (SSD). This will allow the computer to boot up much faster. This may require foregoing an optical drive, however, since SSDs are often installed in the optical drive bay (the optical drive is your CD / DVD drive).
3. While a website like NewEgg.com could be really good for pre-built deals, that will afford you less customization, and smaller websites such as PowerNotebook.com will offer you customized, personal customer service and handling of any issues you have post-sale.
4. I'd suggest setting a limit for the budget that you can live with (e.g. $500, $750, $1000) and then finding the PC with the best specs within that range.
5. Some other factors to consider -- what screen size does she want? 14''-15.6'' is pretty standard, though you can get a PC with a screen as small as 10". Bigger screens will give you more to look at and be nicer to view, but they're also heavier. How much does she plan on carrying this thing around? If it's an everyday thing she may not want a computer that weighs as much as mine, for example. If it's mostly just a desktop replacement, then perhaps she would prefer a bigger laptop. Battery life is another factor. Does she want to be able to use this on the train or bus for hours? Or will it be plugged in most of the time so all she needs is an hour or two at most?
6. I can't really speak to your Windows 8 vs Windows 7 conundrum. I think it's generally safer to go with the older version of Windows, though, if you can help it.