If you buy a Sounblaster Extigy make sure it is a USB 2.0 model. I have an Extigy that is 1.0 USB for my laptop and it's terrible. (for how much it cost and what it promises IMO)
The bandwidth through USB 1.0 is barely enought to playback MP3z that are decoded at a high bitrate if you are doing anything else on the computer throught the USB slots (ie. mouse). Nevermind trying to pass a true digital signal from say a DVD through the USB port. (cuts out alot)
If you can get a Extigy USB 2.0 model then I would highly recommend it as it would then be able to do just about everything someone would need for audio capture/playback.
Thanks for your help, everyone. I went to the site Jason linked to, and the Creative MP3+ is the one that I'll be recommending. I don't think she needs top-notch quality, just a sound card that'll do a good enough job.