Don't do it. She's going to start going to these classes and have all these dudes tell her great job, you're an awesome gal, way to kick butt on those burpes today and then she's going to come home and see you spread out watching an ISU game with your hand down your pants drinking a beer.
Pretty soon she's going to start going out for drinks with her class and within 18 months she'll have left you for one of the instructors that tells her she can do anything, she deserves better and she needs to do what makes her feel good. Then some dude with a neck tattoo will be plowing your fields, Farmin (if you know what I mean).
90% of all my divorce clients started from a CrossFit esque class. True story.
OK, I was laughing at this until the last sentence. Seriously?