How cheap are we talking, here?
You can get computers fully capable of basic multi-track audio recording for like $40 on eBay or at local flea markets (if you have the know-how to clean them up, etc.). $10 monitor at goodwill, $20 used interface off eBay, etc. I would think that's your best bet in terms of bargain bang for the buck. I mean, you could record a few tracks of digital audio on home computers in the late 80's. Just about anything that still boots up would be capable of recording what you're talking about. I just mention this because sometimes people think they have to go to Best Buy and spend $300 to get a computer so they can record audio.
Does she have a mic? You mentioned the iRig PRE, so I assume yes? That seems to go for ~$40, so that sounds like a good way to go, too (not that I have any experience with it.) Especially if she's not already savvy with the audio software world.
Another route could be a portable recorder off eBay. e.g.
this, or
this, or
this. Might be able to find one with good quality built-in mics or XLR-in for like $100-$150?
If she only has like an SM58 or something, the built-in mics on those handheld recorders (or her iPhone, for that matter) will possibly sound better anyway, depending on your goals.