There are some companies that are making bindings that can be used with the burton boards now. I just picked up a pair of the Union Flite bindings, and you can get the special disk to be used with the burton system. Just thought I would throw that out there for you...because I just bought a full set up and looked at so many different bindings that my eyes hurt. lol
Yeah, I was just looking for a board for my sister and we bought her bindings first. Burton Citizens were a steal a colorado ski and golf. Anyway one store had a Burton Lipstick on sale for a steal as well with the EST bindings. We could have ordered a converter for the bindings. They didn't have her size unfortunately so we went with a TWC Burton board, although it's a mens board, it has a great flex and she loves it.
I ride a GNU B-Nice and if she is doing well I would go with a GNU-BPro. A better board with rocker camber rocker instead of just rocker, magnetraction and banana tech. Little less flex but still bouncy. I am not a fan of pickle technology. Another board I really adore, is the Never Summer Lotus but I have never ridden than one.
Good luck and let us know which board she gets and how she likes it.
PS Magnetraction in Colorado isn't as necessary as it is on the east coast but I have hit some ice patches that made me extremely thankful that I have it.
PPS I agree with a previous poster. Go with an all mountain board.