The missus is also your wife's height, so when she needed a commuter bike awhile back, I found a Terry Solstice and rebuilt it for her.

First, these are really nice riding steel frames - sleeper frames IMHO. Hers was Tange Infinity if memory serves.

I always thought the 24"/700c combo looked weird - until I rode one. Then it all made sense. With the smaller wheel, you get really zippy steering. The effect is hard to describe until you've experienced it. The ability to turn on a dime. For shorter riders who've never had responsive geometry, it can be a revelation.

Downside? You've got to stock two different tire and tube sizes, and the 24" ones are not easy to find.

I'd have the missus take a test ride if at all possible. If she doesn't like it, plenty of other options. Lots of used Trek WSD (women's specific design) or Cannondale Feminine frames designed specifically for shorter women riders, and they will be in more standard wheel configurations.