She doesn't really *want* any dog at all.
It's like when we went out to buy my Nissan sports car years ago, before we were married. I asked her if she liked the car. She stared at me with this "I don't want to say what I'm thinking face" for a good 15 seconds and then said, "I like that you like it..."
She may think she hates big dogs, but she knows that getting a dog is what I want most in life right now, and something I've wanted since before we met. So if we do end up getting a dog, she thinks she's going to hate being a dog owner and will only be doing so for my sake (I know she'll love the dog tho).
Problem is, it won't be like my car where all she has to do is walk around it to her own car every so often and doesn't ever have to deal with driving it, parking it, getting gas, changing oil, doing repairs or anything. This dog will depend on her as much as on me, probably moreso since she's going to be at home twice as much as I will be for the foreseeable future.
Therefore, in her eyes this dog ownership stint has to go as perfectly as possible and that means planning for the long run. She wants the dog to be trained as well as possible to be as socialized and obedient as possible from as early an age as possible. And that means a puppy.
Wifeshift doesn't half ass anything or cut corners. Even if she hates doing something, she'll dedicate the time and effort to do it right the first time.