I think you would be better off finding out what she wants to use the PC for and go from there. The system you have is unbalanced with the 6600 and no graphics card so I presume there is no gaming involved.
You may want to look at
this thread that compares a pre-built Dell with a diy build for the same money.
It is surprising how long a machine will last these days. I still occasionally use a xp2800, 512mb ram, xp pro sp2 machine and it will do MS office, internets, email etc quite happily. Machine in my sig is 2 years old (new hard drive) and will be more than powerful enough to last another 2-3 years for the basics.
Would a pre-built be better value for money and less grief for you (tech support) if her PC has some problems in the future?