fishboat

Recently went through this same exercise with my GF. I'd suggest, even if she's delegated the search to you, have her ride the bike before you buy...and have her ride/try a few bikes before that. We tried both bikes you've targeted..even rented a 51cm Dolce(custom fit included) for a day and did 40 miles. When we first started the search I was looking for the best fit for her. I have decades of riding and she had been a runner(marathons, but now 55 years old..and I don't run), but was new to real road riding. I'd ask her, "How does it feel?" She'd say, "Compared to what?..it feels like a bike." After trying out a few bikes, she began to get a feel for "..compared to what?.." She knew when she was too stretched out(eff top tube too long) and when a frame was too small(51cm Dolce). She "came up to speed" on fitting quite fast. Then we tried a 53cm Bianchi Dama. Two minutes after she got on it, she said, without hesitation, "this is it..oh my..this feels great!..perfect" We bought it and she's thrilled every time she gets on it. She's fast..."..it's not me, it's the bike.." We ride together, but just as often she's out on her own..cracked off 36 miles last night after work..got home right at dark as she didn't want to stop and got too far from home.

Long story short..all WSD bikes are not the same. Throw a WSD at your wife that's 'reportedly' the right size is a crapshoot. She may not be interested in the bike, but if it doesn't fit, she will gain an interest, she won't enjoy it, and your local craigslist will eventually have a listing of a nice bike, with minimal use, that is no longer needed..that bike will be her bike that didn't fit.

(fwiw..The 51 Dolce fit her "ok" in the top tube length, but was near maxed out on the seat post height as her legs are long(this also increased the seat-stem drop). The 53 Dama fit her well with seat height, drop, and, with a shorter stem, fit great in the top tube.)