Main use will be: Word Processing and Excel, some Drawing using a Cad program (AutoCAD clone).
I suggested a pre-built HP, Acer or similar PC with a good price / performance ratio but then she replied "So you have a good custom built PC with a fancy motherboard, nice graphics card, SSD, illuminated case with 8 (yes eight) fans and tell me to buy one of those pre-built PCs with crappy CPU and full of bloatware. I want a REAL PC! You taught me that pre-built PCs are crap now don't tell me to buy one."
I don't read many tech articles since the Core2 CPUs but here's what I'm thinking:
CPU: i3 2120 (or i5 2310?)
Motherboard: ASUS P8B75 (my biggest doubt)
RAM: 1x8GB or 2x4 GB DDR3 1333
GPU: Asus Radeon HD 6570 (my wife doesn't play games at all)
How do you plan on backing up her data? If you dont have a plan, and her data is very important, then I would suggest getting two Green HDs and using a RAID1 mirror.
Like Jay said, she only needs 4 GB of ram. You may try to use integrated graphics of the sandybridges. The only problem I can foresee with IG is when using a CAD program with big and detailed objects.
Only one PCI Express 3.0 x16 slot, which would make me slightly nervous. With 4-8GB of RAM, the only real benefit of micro ATX over min ITX form factor is the extra PCI slot, and that board's extra slot is x4. That would lead me to a smaller form factor or getting a better micro ATX board.
Also there is no RAID. On the plus side, the price it nice.