We're all built a bit differently (just as no two men are exactly the same.) My answer is therefore both yes and no. It also depends on the way the pack is built. With some packs, including my own, I'm comfy with a unisex version. With others (my day pack), a woman's version is definitely more comfortable. With others, including Osprey packs for either sex, nothing is comfortable for me! IMHO, pack fit is about as individual as shoe fit.
The S-curved straps do help, all other things being equal--they're a bit more suited to the female anatomy. Another thing that helps is a hip belt whose angle can be adjusted to better fit female hips. Of course, some of us have quite ample hips while others are more straight than curvy. A third item, for those of us females who are "vertically challenged" is the availability of shorter torso lengths. So many pack makers think that a "small starts at 16-17 inches torso length. Sorry, mine is 15 and anything bigger is uncomfortable. (I've seen similar complaints from big and tall guys at the other end of the torso length spectrum!) I wish these options were available from more of our wonderful "cottage" pack makers, although I notice they're becoming more common. My own pack (a long discontinued Six Moon Designs model) has an adjustable torso length starting at 15". I actually think the smallest is 14 1/2" because mine is most comfortable at the second-smallest adjustment.
I suggest you have your GF try many different makes of packs (including some from our "cottage industry" friends, though you have to pay return postage), with her gear inside, to determine what fits her--and her gear--the best. Be sure to include a couple liters of water and the equivalent in bulk and weight of a week's food. I got lucky when doing this--the first pack I ordered, which I still have 7 years later, fit as though it had been custom made just for me--but I was fully prepared to order and send back half a dozen packs if necessary.