Compared to modern tandems it has a very short spacing between the captain and stoker and also a rather narrow hub (probably 120 mm or 126 mm) and it'll be a pretty flexible frame. But it looks like it should work fine if you're willing to live with those limitations and the friction shifting. It'd be best if your fiance is fairly small. That way the limited stoker room is less of an issue and also the rear wheel would be more likely to hold up. We had problems with broken spokes on ours and eventually replaced it with a 48-spoke wheel. I think the flanges on the drum-brake hub were a bit too narrow and tended to fatigue the spokes.

Bargain the price down based on its limitations compared to more current tandems.