Great input, thanks everyone!
About the shoulders; does anyone have suggestions for when their subject keeps readjusting themselves absentmindedly? My wife had to be constantly repositioned because she just wanted to face the camera straight-on with her body. Maybe all I need is more practice so that the gear becomes second-nature, and then I can focus more on the pose of the subject? Once I explained that the straight-on shoulders will make her look more masculine, she seemed to remember a little better to keep them where I directed, but I think she was distracted by mosquitoes. Probably not the ideal location last weekend; mosquitoes have never been a problem there before, but we've had record rains lately.
My goal was to shoot straight-on. Professional but approachable is what I was after- she is starting her own business in sales and this is for her website and cards, so she doesn't want to look subordinate, but neither does she wish to look intimidating. A combination of confidence and amiability is the ideal.
I had her sitting for the first shot and adjusted the tripod to be about even with her. The second photo was with her standing, and unfortunately she is simply taller than my tripod! I didn't really think much about it at the time, probably because I was feeling rushed (she hates mosquitoes with an unusual verve and just wanted to be done with the entire shoot) but it's something to bear in mind for the future.
I think I need a new strobe. I used the same strobe at the same setting in the same location and got a variety of exposures with it. I got it secondhand with my previous camera and it's an off-brand with minimal features, some of which I know do not function properly. I suppose that will go on my ever-expanding Christmas list.
If I can convince her that it's worth it, I'll try another photo shoot at a different location. Good suggestion about it relating to her business; it gives me some ideas too. She seems happy enough with these pictures, though, and doesn't really enjoy being photographed- she just sort of tolerates it when it's necessary. This is probably one of the reasons I'm not more practiced at photographing people. I'll have to use a hard sell if I want her to do it again anytime real soon. But then, Christmas isn't too far around the corner; maybe I can use that angle.