The biggest complaint I've seen about that generation of iMac (and doesn't apply to the 24" models) is that the 20" models use an 6-bit controller, meaning that they are not fantastic for color accuracy. That said it's not a problem for that one as they use the standard 8 bit controller.
The screens in those are pretty nice for photography stuff actually, I don't think she'll have any complaints at all. it's a good fast machine, large and accurate screen and has enough memory and hard drive to keep her happy.