idk since not knowing the snow and terrain conditions...but kids want to hit nelson this winter. A month in the dryer deeper stuff...perhaps more of a powder board. Riding deeper pow is all about float which is different than packed or groomed and it is a different skill set of seeing and choosing lines wisely, pointing it to maintain speed and turning wisely. You can ride a regular all mtn board in the pow with some skills but its a hell of a lot easier on a pow board with a shovel rockered nose, and cambered pin/taper tail. However being circus performers...i can only imagine...assuming having a good body mechanics and awareness...go for an advanced level board like an envi or bpro and perhaps if her weight and boot size allows go for a small mens board like a rider's choice, bsod, charlie slasher etc.
Great suggestion picking up a smaller mens board.
Are you looking for strictly a pow board for this trip? Knowing what your home mountain is would help, if you want to buy a new board to use all the time, or like i said if you are just getting a board to use for the pow trip.