I have not read all the responses so I may double up on things.
Take her to Boulder Mtn. Maybe just the cabin the first day. Let her play for a while at the cabin. And rest, and warm up. Don't forget to sign in and on your way back, sign out.
She will get stuck, if she does not, she is either better than you thought or she is not out of her comfort zone. DO NOT GET UPSET WITH HER. Even if it is over and over and over, and you would love to say some stupid male comment, you bite your tongue and continue to encourge her.
One of the most difficult things for me to learn when riding in the mountains was to stand tall to turn the sled. You made an excellent choice of sleds, but she needs to understand that even though it does not feel right, nor as easy to stand tall and turn the sled, it really is a lot easier than trying to wrestle a 500 lbs sled. The sled wins, she loses and so do you.
Balance on the sled is key past the cabin. She will need to be standing a lot and she needs to know how to work the sled. There are some pretty good hills that she cannot avoid and she needs to just go for it. Hesitation will cost her.
Remember you are taking her, so she comes first. Better get used to the fact that women are always first.
I am jealous though, I so miss Revy. But husband has almost everything done; he should have his 10 yr greencard by June as well as my passport, so we can head back across the border for some sweet, incredible June riding for my birthday again. Although he wants to head to go to AK, which would not be terrible, just a much longer drive.
Oh ya, take a GPS and know how to use it, along with beacons, probes, and shovels for each of you. Safety first.