You linked me to the main page, not the page for the computer itself. Regardless, like I said, I probably wouldn't pay anything for a computer that old. If I did it wouldn't be much.
If it's your money she's trying to spend you can make the call and tell her PC or she has to find a better Mac. My 2 cents. A computer that old, even if it runs ok (which is highly questionable), could still have a component fail at any time. Better off with something new.
I've got a laptop that is probably about 10 years old I rarely use. The processor may very well be less powerful than the Mac she is looking at (it was far from top of the line when I bought it), but it's essentially worthless nowadays. Struggles just browsing the internet.
Sounds like she's been brainwashed into the cult of Mac. I'll give Apple credit, they did a good job with that.