I ride my GNU B-Nice with Burton Lexa. She might be a newbie but don't go to soft on her or she will grow out of them super fast. I'm only 12 (?) days in and I have gone with a stiffer board and bindings already. Of course, I love the GNU still and ride it every time. I adore Flows or any rear entry binding, although you will be find very different opinions of them here. GNU makes great bindings that are super cute (if she cares about that kind of stuff) in all price ranges and flex. Because the board is SOOOOOO flexible get her a mid range binding in terms of flex. It'll give her more control.
Hope that helps.