Depends...
Depends on a few things, as I'm sure others here will say too. If she needs the computer now, and she's just using it as a general purpose computer (Internet, iTunes, Word Processing, etc.), which I'm assuming she will be because she's looking at the iBook, there really isn't anything wrong with getting it now. If she has the time to wait, I'd suggest waiting to see what comes out. If the new iBooks (or whatever they'll be called) are at a similar price point, I'd get one of those. Basically, if the iBook will do whatever she needs it to do now, it'll do whatever she needs it to do in a couple of years too, but I'd still rather wait and get the newer model if possible.