Keep an eye on CL. You can get G3 imacs for $20-50. If it is above 333mHz then it may be worth the little amount of cash for what she needs it for (we have a 333 in the office for the interns and it works just fine for database, wordprocessing, internet, and itunes). You'll want to make sure it has at least 512mb of RAM (Igb is preferable), and I suggest Panther over Tiger, as Panther has all the speed upgrades from Jaguar with less resource drains than Tiger. You'll probably also want to swap out the hard drive, as it is probably a 5400rpm drive. Swap it out with any 7200rpm IDE drive under 120gb (that is the ceiling for the later models; the earlier have a boot drive ceiling of 8gb, but you can create partitions to solve that in larger drives, and you should probably avoid earlier models anyway).
The easiest way to tell G3 imacs apart is the optical drive; if it is tray-loading, then pass it by. If it is slot-loading and at least 333mHz, go for it!