We’re leaning towards belts, but she’s concerned about them rubbing on her hips – any female-specific (for those with narrow waists and significantly wider hips at least) belt designs/brands out there?
I’m not sure whether that’s really an issue*, most of the material is at the back (above your bum) and not on the hips. That said, Salomon has a variety of models, I’ve got a Sensibelt which has more material on the sides, there’s also the Hydro 45 which has a thinner belt. I’ve not tried this particular model, but I have used belts with this style of strap.
I’ve never had any problems with rubbing, and I’ve used quite a few different models, although I’m not a woman so my experience is obviously not entirely relevant to your wife’s question.
* if your wife says it’s an issue, it’s an issue. I realise this 😉