Weighted is good as it feels like and actual piano, so it's then easier to play a real one after learning on the keyboard. Piano keys feel heavier and sort of harder to play after non - weighted keyboard keys, sort of like typing on a clunky old keyboard after getting used to one of those lovely flat ones that come with an iMac (or not really, but that's the best comparison I can come up with..)
If she's just beginning that slightly shorter Clavinova wouldn't be the end of the world as easy pieces tend to stick to the middle anyway.