Good grief, just get her a decent Intel 865 board, with a Celeron 2.8GHz or P4 3.0Ghz (non-Prescott), and she'll be more than satisfied. Heck, she wouldn't even notice the difference between a 2.0Ghz and 3.6Ghz if she's doing basic office/email stuff, and it's a huge waste of money.
Plus, upgradability? In this day and age? Don't make me laugh. By the time she wants to upgrade, she'll have to change everything, and that'll be a good few years down the road yet.
Bottom line: Intel board (D865-GVSRL should do it, Video, Sound, LAN onboard), 2.8Ghz Celeron/P4 Northwood, 256Mb-512Mb value PC3200, 40Gb HD, CDRW drive, bosh. Done.