Oooo. I can already see a large debate with this thread.
I'd go with the WiFi version, 16 or 32GB, depending on how many songs and such she'll be downloading onto it. May as well go with the iPad 2 version too, as it does include the cameras for FaceTime, which is pretty good.
The new model includes things (like the camera) that really should of been on the first one. Most reviewers with inside industry information are saying that this is really iPad 1.5, as the next one will have bigger changes. The iPad 2 is really an update to the iPad 1 with missing features, but is it worth the money? Depends. If you don't have an iPad, go with the iPad 2. If you do have an iPad, wait for iPad 3.
I'm holding off on the tablets because I really couldn't justify needing one. I don't do a lot of business traveling, and when I do, my laptop more than suffices for my needs (long battery life, I can play WoW on it, etc.)
I think having an iPod touch throws a curveball to the question, wewo. Should you buy an iPad for her when she has the iPod touch, which more than suffices for most of her needs? That, I cannot tell.
Final judgment: If you have the money, and don't mind spending it as an entertainment device primarily used around the home, and maybe at school (during lunch or after school), buy the iPad 2, 32GB WiFi Version (unless 3G is ABSOLUTELY necessary). If you got an iPad already, hold off on it, as buying a new one to replace the original isn't really justified for the cost.
Note: Be on the lookout for the other tablets, such as the 10.1 Galaxy Tab from Samsung, or even the Asus EeePad Transformer, as they may match what she wants, and could be a better experience or price. (Before anyone rages, I say COULD, not IS)