Welcome. I'd bet the tires will fit. I've got some 1.25s on normal MTB rims.
Buuuuuuuut...
Originally Posted by
aristotle13
So I'd like to convert my old MTB for my wife so she can have the best chance of keeping up with me on my road bike, and I'd like to keep it low budget for now...
Depending on how the ride goes, you stand a good chance of putting her off riding forever. Roll the dice.