I've been riding my road bikes for years and my wife gets jealous of my time. I've offered to get her a road bike, but she does not like the gears .....and she's slow. Real slow.
So, to insure marital bliss, I figured a tandem would be good.....but what if she does not like it?
I found a $200 Tandem on Craig's List........a Miyata DubloCross...more of a "mountain" type than a road one, perfect for level bike trails.
And yes, it was in ROUGH shape. So far I have replaced the chains, rear deraileur, brakes, tires, all the cables, & seats. The bike was not used for many years, but it was strored under a tarp in someone's backyard.
It will be another week or so before I get it in ridable shape - but the frame & wheels were in good shape so I figured it was worth the $200.
So far I have about $400 into it, between the original cost and the associated parts.
I'm sure your wife is slooow at the moment, but get her into riding regularly and she will probably make quick progress, either on a tandem or single bike.
My wife started by coming out on a university club saturday easy road ride on an MTB with knobbly tyres, mudguard and d-lock wearing trainers, jogging bottoms and a sweatshirt. My friend Steve had to split off to accompany her and took 3 1/2 hours to do a loop that most do in <1 hour.
After quite a lot of training and 3 years she won the UK student pursuit championships, and competed in road races, track and time trials, winning a lot more than I ever managed.
We still have laughs with Steve about that ride. He normally maintains that it nearly drove him to give up cycling and walk home/ contemplate killing himself, depending on how much he's had to drink.