I have personally been down this road. First with my wife and now with two little girls. I think the responses so far (although a little sarcastic) are on the right track. If you want her to get interested in fly fishing for the long term I would not start her out in the winter on the Spokane's icy rocks. If you're going to do it, then keep it short and sweet and take her out during the warmest part of the day and then do a nice lunch and some drinks. If you can break away for a half day I would hit up Rocky Ford. Being able to see the fish goes a long way towards keeping a beginner engaged. Fish a little bit in the middle of the day and then hit Chico's on the way home. Either way, good luck. Take it from someone who has been down this slippery slope.