im guessing your GF?
dont teach them how to ski.  learn how to snowboard with her.  that way both of you suck(you probly less so cause you know how to slide on snow)and neither of you gets frustrated with the other.
it will be a learning experience, and both of you can feel on equal playing fields instead of her getting pissed at you for not being helpful and understanding enough, and you getting frustrated with her for her utter lack of anything resembling athletic ability.