AMD fx 4130 3.8ghz $99.99
ASUS m5a78l motherboard $44.99
Crucial Ballistix Sport (2x4gb) $76.80
NZXT Source 210 $32.00
Corsair cx430 $39.99
Western Digital Caviar Blue 320gb hard drive $38.40
Total: $332.40
All parts from Amazon. If you can find them cheaper then go for it. I would have gone for the athlon x4 750k but it's not as fast as the fx 4130. If you want you can get either the fx 4130 or the phenom ii x4 965 black edition. It has come down in price to 100 dollars. You can get the 6300 and spend 20 dollars more, but if she is only playing zombies then the quad core fx 4130 should be fine. You would want the 6300 if she was doing a lot of next gen gaming.