I wish this style of frame was more available. Yes, I do tour on a 'women's bike' AKA mixte AKA step-through-frame, and I really prefer it. But to get my bike I ended up having a custom frame built for me.
Here's a photo:
In addition to being able to step-through the frame the generous stand-over height is a real plus.
As you can tell from the photo, I'm far from an ultra-light tourist. I've never had any concerns with stability with the frame, and I've gotten pretty close to single-track mountain bike terrain with it, fully loaded.
As Americans begin to ride more for basic transportation and the baby-boomers (hi gang!) continue to age, I think this style of bike will become more popular. When I'm in countries where people use their bikes on a daily basis, I see very few 'racing' style bikes and a lot more step through frames. Actually on one tour a German man came up to me and after discovering that I was American asked me, "Das ist ein Amerikaniches Fahrad?!?" That's an American bicycle? I pointed to the 'hand-made' decal on the front tube and he understood.
If your friend's bike can mount racks, is comfortable for a day in the saddle, and has (or gets) the proper gearing, there's no reason to fear the step thru frame.