AfricanTech
Honorary Master
Unless she has been using a PC regularly for all her daily tasks, and has got used to all the idiosyncracies of a particular version of Windows, and can navigate her way around it comfortably, get a Mac. It's really hard to go back to Windows once you are used to the consistency, stability and ease of use of OS X, particularly if you are a normal user. A new Mac will perform spectacularly better than any five year old machine, although as has been noted, it's testimony to the design that a machine that old is still quite usable. Don't ignore the advantage of the integration with the iPhone and iPad, especially now with Yosemite and IOS 8.
This is my main reason for seeking other opinions - the integration would be great plus I really like the convenience and ease of use of Time Machine - it might sound silly given that there are backup solutions for Windows, but nothing compares to the ease of Time Machine.
There are other little things like being able to boot off the external drive, etc