People (including the female variety) are either adventurous or not. My current (4th and final) wife is a backpacker, caver, kayaker, backcountry skiier - you name it. When I met her 12 years ago, she didn't know I was 'between motorcycles'. Then, I came home one day with one and she was aghast. She had never ridden one and forbade her sons from riding them, believing all the nonsense that's out there about the danger (well, maybe not all nonsense). Anyway, she tolerated what I thought would be a solo experience until she discovered from one of the gals in her office that there's a whole social world out there around this sport and that not all 'ryders' fall into the 'biker' category.
In other words, with experienced and responsible riders, there's social acceptance, even pride, in riding and touring particularly. So, not one to be left out, she went with me on a 4-day ride with the local motorcycle club to Jackson, Yellowstone, Targhee and back to Park City and she was HOOKED! She's been riding with me ever since and this year got her own Spyder (the Cognac one). Her family is amazed and impressed, particularly her sons and grandsons, who have yet to take up ryding (but you know it's just a matter of time).
Anyway, if your wife is adventurous AND she feel confident in your ryding skills AND she doesn't want to be left at home, she will come around. It helps if someone in your social circle also rides. Otherwise, spare yourself and your wife a lot of grief - just go on some 3-wheeled adventures solo each year and be grateful your wife is understanding of your passion.
