Your wife is a tool. End of story.
(Sorry, no disrespect, but seriously, she wants you to buy a bike based on how she thinks you look on it? Get a grip!!
)
There's a guy on our local board who's in his early 70's who still rides sportbikes. Not just rides, but collects and races. He's an incredible rider, and everyone looks up to him; and NO one would ever say he looks "silly" on a sportbike or that he's too old and should get a cruiser.
Get what you love and tell her if she wants a cruiser so badly, she can get one for herself.