Skimmed the thread so correct me... I saw a lot of numbers but not the one that matters - inseam. What is her inseam? I'm 5'3 117 w a 28.5" inseam. Personally, I hate cruisers, don't care if they're low and light. The way they make one's posture sit back and kick your feet out, it is not a good "ready" position (been an athlete all my life so knees bent on the balls of your feet is an ingrained, strong, physical posture for me). Sounds like she's of the athletic type too, I'm not too concerned about her coordination or strength working a bike, she just needs to get skilled at moving around a bike.
First thing's first though, get her into an MSF class. Those are your basic skills for life - period. She has the opportunity to learn on a bike that isn't hers and she doesn't have to worry about dropping/scratching breaking or even investing in. From there she is MUCH better prepared to sit on bikes and pick one out that is comfortable for her. Don't pick out her bike, let her do it, just present her with the appropriate options.
Remember, this is her first bike, not her last. She can sell/buy when her skills and mind are ready.
My first bike was a Japan spec VTR250 in '07.
Best bike I ever had. Since I lived overseas at the time, I had to bring my own bike to the MSF course. Plus I had to modify it to ride but that's another story. It was enough power for the street (there) and low enough seat height after a shave. Here in TX, I'd say look for a 250-500cc bike but I'd aim for over 300 to have enough juice if she had to be on the highway. Weight and wind will be a factor on ultimate top speed but she needs to have enough power to get out of trouble. The equivalent bike here in the States is the Honda CB lineup. Check out the Kawasaki Ninjas too. There are some smaller capable bikes, but what you'll run into is seat height/inseam challenge. I would ain to find a bike that is fuel injected...ie, bump up your shopping price. Fighting with a carburetor when you'd rather be riding is frustrating,
trust me.
All that mentioned about a street bike, consider dual sports too. They'll be relatively tough and resilient to drops, bumps and bruises. Plus you can find them at reasonable prices. Look at the XT225/XT250, Yamaha WR250R, Kawasaki KLX250, Honda CRF230L/250L. Unfortunately you will give up top speed and they're not going to be suitable for highway speeds (sans the WR250R, plus it's taller).
My second bike back stateside was an SV650. It was a ton of fun bike, super torque motor and ran like crazy. But while I loved the pull on it, it was a bit topheavy for me and I never really got comfy on it. Didn't stay on that one for long, literally. It's a great bike, just wasn't the bike for me.
If once your wife gets through the learning curve, check out the street bikes in the European/Asian market. They offer sub400cc bikes to compete in the tiered licensing system those countries use. I've been eyeing hard the BMW G310GS but they make a street version G310R which is a little lower seat height. Another is the Ducati Sixty2 Scrambler redo.
Right now I'm tootling around on a plated TTR125LE. My intention was to get my skills back underneath me after being off a motorcycle for a # of years. I'm also drifting into to dual sport riding, so I'm going easy. Traffic is nasty out here and I intended to stay out of it, but I find I'm getting back into it more and more.
Personally being a small chick I don't need a lot of bike to ride me around, <700cc moves me just fine, just a matter of finding which way I wanna be moved around is the question. For your wife, get her basic skills laid as the foundation. Do that on her first bike, after that, shopping is more wide open. Remember, her first bike, not her last. Or rather, she can collect many, like shoes or purses.