i taught my gf to snowboard (which i dont do, we just figured it out), and she didn't ski or skate or do anything at the start. 5 years out we're married now, and she's really good, so it is possible
Like most have said, the key is PATIENCE. She won't be able to keep up with you, ski the fun stuff or really do much of anything at the start. You will spend most of your time with your skis off. You've got to be understanding of this, its not her fault, its just part of learning from scratch
My recommendations: get her out as much as she's willing to go, don't take off on her to ski park/pow unless she recommends it, and once she has the basics take her on long cruisy runs. Bunny hills are fine, but getting on and off a lift is always an unnecessary struggle, and when you only get 2 turns in top to bottom that's not much room for improvement. Long cruisy runs give people an opportunity to focus on figuring out how to ski and giving them lots of time for on hill practice, rather than struggling with lifts
i'm not gonna lie, it's a huge investment to make, but if she's worth it than make it. Remember as well, as much as you've gotta be patient, she's gotta have a good attitude, if she doesn't want to progress then she wont