You can find a used iBook G4 on ebay for less than $200 these days.
Very easy to buy one, do a fresh install of OSX, then use the Apple Migration Tool to copy over all her settings, applications, documents, etc. It's a very easy process in case you've never used the migration tool before.
If your handy with a screw driver, you can buy the 1 GB ram upgrade (max) for ~$35 and a nice new 80 GB hard drive for ~$50.