I saw your posting on rec.windsurfing and provided my perspective there.
For anyone else interested in the same information, my perspective is that a harness is a very personal choice because most of us women are put together a little bit differently from each other. One has to TRY a harness on, in the store, AND on the water, to be sure that it not only fits, but is comfortable, and comfortable for more than the first 20 minutes.
I am a confirmed seat harness person, having not yet found (after trying many) a waist harness that does not ride up, squeeze my ribs to the point of major discomfort, make my lower back ache, etc.
I am "short waisted", i.e. high hip bones and not much space between hip bones and bottom of my rib cage. The wider the waist harness, the more it jabs me in the shoulder blades. My hip bones make the harness ride up. If I get it tight enough to keep it in place, I can't breathe.
If a woman has a long torso (or at least longer than mine!), she may well like a waist harness.
I also sail on larger sails, and in light/marginal conditions, and a seat harness is often better for that. But even in high winds, I'm happy with the seat, probably because I've used one for ages and my body *knows* how to use it.
Windsurfing should not be about "enduring discomfort" so I keep using my seat harness. I use my legs (which are strong) and the seat harness suits me just perfectly, even in high winds. I can position it so the hook is at my waist but the leg straps will keep it down. I can breathe and remain comfortable.
I've demo'd many waist harnesses, and owned 4 or 5, but not found one that really suits me. I've also been through a bunch of seat harnesses, but found that I had to be careful of how the leg straps work as a few of the ones I have tried would not allow me to be as flexible as I'd like when waterstarting.
good luck, and my sympathy to the lady. Sail near me and she could work through my collection of old harnesses!