You are getting some really good advice on this one, but I think Kneale and someone else touched on going out to a small area, locally first. This will give her an idea of what to expect, and a much desired head start, prior to going with the group.
And undoubtedly- don't try to teach her yourself!
That is without a doubt, a major recipe for disaster! You may want to consider finding her a female instructor to show her the initial steps.
And certainly make sure she is warm, and LOOKS GOOD! Come on ladies! You know that looking good is almost as important as being warm! It improves confidence, and therefore, performance. Guys are no different, but to us, it's our equipment. Do you ever ski better than when you are on new skis?
Set her up, buff her out with great gear, and show her that enjoyment can happen at ANY level of competence!
Hope you both have a great trip!!!