Why - when the 4 is out?
If budget is a concern, go for the 2. If it's not, go for the 4 ("iPad with retina display"). The worst choice would be the 3 ("new iPad"). The 3 is not a bad device at all, and it was the right thing to buy 6 months ago, but it's not today.
Get the 4 - no difference from the outside (other than the lightning connector), but significantly beefed up internals.
If she doesn't need the size of the iPad proper, consider a mini and save yourself some cash.