Great news! You have a wife who either likes spending time with you, or at least tolerates you enough to ride bikes with you.
Step 1 out of the way.
Does she still complain about the bike after you put the cruiser(ish) bars on it? If she sits bolt upright, maybe she needs a cruiser(ish) seat also?
I guess if it’s her bike, your opinion of it isn’t all that relevant.
Maybe put balloon tires on 26” wheels on her Linus? There you go- if they fit I just made you a step-through mountain bike.
I need to get my wife a step through bike.