My daughter is the same size she has a 144 for a jib, 148 stiffy cambered for a bomber and 155 for deep poo. She is athletic, loves speed and easily hits 45-50 mph on the 148....infact she thought its not big enough cause she maxes out. So in an effort to go faster shes switched to skiing fatty twins...last year on 169 k2 misdirected and this year on some surface skis that are 174cm and are 121mm underfoot and 154mm at the tips. Its not the board...its her determination and aggressiveness. The 148 b-nice should be just fine...especially if she likes to bomb.
bomb on skis
messing around on her 144