Depending on what she does with it, I would even look at putting a 5400rpm drive in it for less power draw and cooler operation.
Also, I don't know if a Mac of that vintage is compatible, but SSD drives are reaching a workable price point. I recently built a couple of field systems for work and a Foxconn mini barebones system for myself using SSD drives. Sure, you're still not getting as much storage for the buck as an HDD, but they're fast, quiet, use little power, and are physically tough. Small HDD USB external storage drives are dirt cheap now, so getting a 60 or 120gig SSD plus external storage will still get you a ton of space. May be more than you want to spend, but is something to consider.