My suggestion is to forget Gnu, for now. While their boards are generally very good and draw stellar reviews I find that beginner women riders struggle a bit with Magne-Traction and find it hooky at speed. Gnu boards are also pretty wide and with your foot size you'll find them a bit harder to control. I would also stay away from anything rocker-shaped especially if groomers is what you have in mind. Stick with rocker/camber profile. It is stable, doesn't catch easily and gives you good pop to enjoy your rides. You also don't want anything super-flexible or super-stiff for all-mountain riding. A flex of 3.5-4 should do.
All this being said, I'd recommend a Burton Feelgood Flying V, Burton Lip-Stick or NS Lotus. I think you should stay in 145cm range but I wouldn't go lower than 145cm, because once you gain enough confidence (and speed) you'll find yourself washing out of turns with short board.
Hope this helps.