Or what you could do, assuming the hard drive you buy has it, is mirror all the info from the old drive. Aside from the OS, it'll be a mirror copy of what she had on the prior drive, of course the external enclosure method works too, and you get to ditch a lot of programs you meant to delete or whatever anyways.
So just to clarify, she has a monitor and an OS, I'm assuming keyboard and mouse too? Basically we need to work on making a pure system for her.
Case: $48 Luckily, if you order it today you get their "Shellshocker" discount on this fine case:
Antec 300
There are cheaper, however after you factor in shipping for most of them, it turns out just a tad under ($10 in the case of the cheapest) but Antec makes some very nice cases with awesome airflow, plus if she ever wants a stronger system, this case should still be plenty fine for high heat components.
PSU: If you want a high quality PSU: $60
PCP&C 410w
However if you're looking to put money towards a different component, not sure how their name is here but I trust OCZ so: $25
OCZ 500w
Same price up front for either, and both are free shipping, but the OCZ one comes with a nice rebate.
Ram: $23
OCZ 4gb set Ram is just one of those things you just opt for the cheapest, assuming the company isn't infamous for some reason, and this is the cheapest 4gb set (after rebate of course) Newegg has to offer at the moment.
Now the part that makes a difference, Intel or AMD for the cpu/mobo. I'm not really sure how every AMD cpu stacks against Intel's, so I'll give you a configuration for each here:
Intel Build:
CPU: $83
E5200, sure the E2xxx series is cheaper, but I feel for the price difference and the performance difference, unless you're on a super tight budget (in which case you'd go AMD) this is one of the best values in terms of CPU price/performance. The next step up would be the E7200, then the E8400.
Motherboard: $45
Foxconn GF7050, in my eyes the best value for integrated if you go for the Intel chips. I'm considering getting this board myself for an HTPC, excellent reputation/looks/price. You can also always pop in a video card if you ever feel the urge to game. Also, there's a 7100 version for $5 more if you have a use for HDMI.
AMD Build:
CPU: $53
Athlon X2 5000, this seems like a decent chip in my eyes, haven't worked with AMD builds in quite some time though so someone who's more thoroughly versed in the AMD chip hierarchy might suggest a different chip.
Motherboard: $40
Foxconn A74MX-K, what can I say? Foxconn seems to be the absolute best choice when it comes to price on motherboards with igp's. Room to upgrade with the CPU/video card if you so choose to.
All prices are after rebates (if any) and none have any shipping costs. Either build would probably be more than adequate for what your gf intends to use it for, I mixed in a bit more power though in case you ever feel like gaming with the system. However if this system is purely meant for web surfing/light media, I could build it even cheaper probably.
You could save $13 on the ram for example, if you choose to go with a 2x1gb set instead of 2x2gb. The Intel CPU can be downgraded and save you about $13-16 (even more if you consider using the Pentium Ds). Doesn't get much cheaper for the PSU/Case on their own, but if you don't mind using Rosewill for both (most don't trust the PSUs) then there is a cheaper bundle on the Egg. You could save about $17 if you downgrade to a single-core for the AMD, $8 if you downgrade to the cheapest retail dual core. Motherboards are the cheapest around though, not much to sacrifice there.
That's my build suggestions thus far, hope it helps you decide/build if you do decide to do it yourself.