To me, for someone who only freerides (groomers, trees, powder) doesn't do any freestyle the Burton Blunt 147 is an awfully soft/short board for someone at 125 lbs.
My wife is 5'0" 95 lbs and she is riding a 146 cm board
. This is a video of her riding a black diamond slope (Chair 4 at Kirkwood) halfway through her third season of snowboarding (about 15 days a season).
She will be the first to tell you that she isn't athletic - doesn't go to the gym, doesn't really do any sports (although when we first met I told her she would probably have to learn how to snowboard
). She actually gets winded tying her boots and walking to the lift from the parking lot... but I think she does a decent job of managing that board.