Honestly, forget soundblasters.
M-Audio had a nice 1 in 1 out soundcard that would be ideal for her. I am a DJ and also know about studio's and recording. It's called the M-Audio 2496 i think, simple card runs under 100$ US I was going to pick one up a while ago. To trained ear like me, i can tell the difference between a soundblaster and a decent card by far.
You will also want to get some sort of a mic pre-amp. I was reading about a good deal on some kinda pre-amp a while ago in my magazine. A cheaper alternative would be a behringer mic pre-amp, and their half decent and VERY cheap.
You would also need a half decent mic, one of my favourite mic's is a shure SM-58 which is very good for alot of applications, but im not 100% sure if it would do well for piano, but some people use them for piano. Should be aqquirable for 80$ USD
Now you need some software for recording, some things that come to mind for simple recording are Adobe Audition (multilayaring capabilities, good program) and Sony soundforge (no multilayering)
If she writes music on computer, I am not sure of the programs you would need to do this. If you want I can dig up some links as well