any PC will do! Build her a cheap one around $200-300 and keep the profit, hehe. Just kidding. She'll get pass with using the Athlon XPs. THey're very affordable.
Actually, maybe it will be cheaper if you just got her a completed PC and get it retail off of some websites. One of the lower end ones. She'll still be able to do what she want to do on the computer. Most come with monitors, speakers, mouse, keyboard, and even a printer. The costs are like $399 which isn't bad for a complete system.