I have a 4S and a love it, and I see no reason to get the more expensive 5 model at this time.

The biggest difference between the 4S and the 5 series is the docking/charging connector plug. The 5 uses a brand-new plug design.

The new plug design isn't an issue for her because she's starting from scratch: She doesn't have a ton of existing charger cables squirreled away all over the house/work/suitcase/laptop/desk/bedroom like I do, and doesn't have a custom hand-made car dock using the older plug design like I do. Me, I'm sticking with the 4S as long as I can so I don't have to throw away all my existing infrastructure.

The 5 series does have some minor technical improvements, but I'm not convinced those improvements are worth the extra money right now. The 4S is great.

One problem with the 4S is that, if you buy one new from Apple, you can't easily get the one with a lot of disk space. I got one with 64GB of space, back when it was the newest model (and spent a pretty penny doing so), but now, if you want to get a 4S because they're the cheap "last year's model" now, you can't get a 64GB model, they only sell the smaller models now.

The disk space is necessary to store downloaded apps, pictures/videos you take with the phone's camera, and iPod songs. If she wants all her music on the phone, look at how big her MP3 collection is right now and see if the existing model will suffice.

(Wow, remember when the Empeg was the only thing with enough storage to store your whole music collection? )