It's all depend what she got really, is an old imac G3 or is it the new imac G5? Saying you got an imac is like saying you got a compaq... What is the processor and how much ram? If you don't have a clue, check "about this mac" in the finder menu.
2 years ago, I tried an ibook and a powerbook when it was time to change my G4 tower for something more portable. The ibook wasn't even able to load my not so power hungry tracks. At that time ibooks were G3 tho. I bought the smallest powerbook at the time, a G4 667mhz. The ibook is always the slowest mac available...