Take her to a good store with lots of selection and have her properly fitted for a pack. Try them all with a load in them. Let her select the one most comfortable. Whether you buy it there or purchase online later, getting the pack with right fit makes all the difference in the world and it's more than just a matter of height.
The hip belt is really important. That's where the weight should rest and a woman's hips greatly vary. Until we're carrying that loaded pack, we don't know how it's going to feel.
I once bought a pricy new pack online right before a big hike in the Bob Marshall Wilderness in Montana. I came back with large bruises on my hips. I was in complete misery. I will never make that mistake again.
Even though you don't plan on her carrying much weight, it can always happen. If you twist an ankle, she would have to transfer the load from your pack to hers. So you may want to just get the right one in the beginning.
Here is a good link for how to measure torso length to assist you in selecting proper size for her:
Hope this helps.
Another thing I've found is that packs for men tend to have shoulder straps that are really too wide for women. Our shoulder and chest areas tend to not be as broad, and we also have breasts to factor into the fit. With the wider shoulder straps, they tend to cut into the sides of our neck and cut into the sides of our breasts and armpits. NOT fun!Hip belts for men often don't fit comfortably on our hips. Quality packs for females will have a canted belt. That's where the weight should be carried and if the fit is off it's really miserable.
Same here, Maurepas. Many of the outdoor retail type packs nowadays are made of durable materials, and many don't weigh a ton when empty. There are plenty of people out there each year hiking for months on end, day after day, using these packs. To me, that's a good testimony to durability and function.I've never been able to find a decent fit in a military pack. I also find them heavy as compared to commercial packs with the same carrying capacity.
+1 on the Kelty.