It's important that you have all the "logical" items tied up, like whether you can afford it. But the selling point in any major life decision has to resonate emotionally with a person. The have to "see" themselves after they make the decision. Think about buying a home. You might work all the numbers to see what you can afford, but when you actually decide on a home, most of the time it is because you can see yourself living there, you like/love a particular feature, you say to yourself "we could do this ...."
It will need to be the same thing with spouse. Neither one of you will buy
DVC because you can afford it. Think about the deep down reasons that you really want DVC. If those will resonate with her, share them. Take some time to reminisce about previous trips to Disney, look at old pictures. Talk about what it would be like to go every year or every other year or more that once a year. Figure out what her most favorite things about WDW are and discuss the fact that you can do them most often.
Talk about the rooms - "wouldn't it be nice to have a full kitchen". Talk about touring style - "wouldn't it be nice to visit a park and only watch the live entertainment, no rides" or whatever non-commando style appeals to you. Talk about the theming of the resort your looking at. Talk about things you have never done at WDW because you've never had time. These boards are full of great ideas. Create a picture between the two of you that puts you right there on your vacation. Create ideas about a tradition for each new trip (eg. every trip we're going to eat at a different pavillion in EPCOT or a different resort) so that you create the image that going back over and over again is exciting, not boring.
One of the DVC booth people talked to us about Food & Wine, about high tea the GF, horseback riding at FW, watching the fireworks from CR, renting a poontoon boat. We'd never done any of those things before we bought DVC, but they created good feelings in us about being able to do them.
If she can't do that, or doesn't find that picture appealing, IMHO you need to think carefully about committing to DVC for fear that you have two very different opinions about the wisdom of you buying DVC.
I'm sorry if this is an overly long post, but this is the type of thing I feel strongly about. It is easy to concentrate on the "cold, hard facts." These are important to take care of, but they will not be the reason you buy, nor will they be the reason you love DVC.