But seriously, I second indy's suggestion of trying on a variety of brands and sizes, ESP when helped by a reputable shop. REI is a great source if you get one.

Tho' I also question the need to spend $ on shoes solely for winter MTB at your current level ( or mine for that matter). Black ice, frozen ground just adds to many hazards if you are already concerned about falling and not comfortable with the drop offs next to trails. Isn't there some MUPs you could ride instead? They shouldn't be crowded with either bikers or pedestrians in late fall/ winter.