jeez Legion...could you be any more misinformed?
Get her an iPod nano. $199. You can spend less on the Shuffle ($99 or $149) but the nano is tre cool.
No you don't have to rebuy your music. You can rip all of your existing CDs and transfer them seamlessly to the iPod. You can also buy new songs from the iTunes music store. The AAC (mp4) format sounds much better than mp3 to my ears (unless you're using a high sample rate). And while wav (or aiff) sounds great, files are huge. But iPod will play those formats too...
iPods are seamless with Mac or Windoze...iTunes is very well designed software and runs the same on both platforms.