Take a look at the Giant/Liv Invite. It's a women specific adventure road (gravel?) bike. It has tire clearance of 42-45mm front and 35mm back (according to the person of Liv Cycling USA who answered my FB message about this topic).
I don't know if your wife is as 'vertically challenged' as I am (5' even here), but that model comes in smaller sizes too.
I *really* wanted the Invite for myself, but the distributor in my country won't order it as there's no market for it here. But so far, I've read great reviews of it, so it might be worth a look if you have a Giant dealer near.