In reply to felt:
> ISM is often recommended.
I had an ISM saddle for a while - it was OK in a time trial position, but if you sat up at all it was agony. As a saddle on a regular road bike it was purgatory. The only positive is that I sold it for what I paid for it. Each to their own, of course.
To the OP - It might be worth looking at Fabric saddles - I have them on three bikes. They have the great advantage at least of not being expensive mistakes. They come in a range of widths, curves and padding types. I'd be inclined to find one that suits your wife and then see what you think.
The other thing to consider, which may not apply, depending on your respective styles of riding, is that it is a saddle not a seat. There's a difference. Finally, and as previously suggested, you could buy an extra seat post and one or two Fabric saddles for less than any other big name saddle - you're going to have to adjust the seat post every time anyway I would have thought