Actually, youre on the right track, Andrew. Im assuming a few things, such as youre hiking in Washington state, you read weather forecasts so have a rough idea of what to expect, and youre staying below 5,000 feet (generally). So your friend will be carrying a basic clothing setup, some of the food, some water, a light sleeping bag, and a sleeping pad. Terrific guy that you are, youll be lugging the tent, stove, cookwear, most of food, and so on.
A 3,000-cubic-inch pack can easily handle what she needs to haul. And the Osprey Aura 50 ($199) is just that size. Its fitted for a woman and has lots of pockets and compartments to keep gear organized. And Osprey suspensions are first-rate, comfortable, and easily adjustable. Gregorys Jade ($199) is exactly the same size and also designed for a woman, so if you have a chance to look at the two side by side, do so, and have her try them on for fit.
For something just a little larger, Marmots Diva ($199) has 3,400 cubic inches and lots of external tie-down points for extra gear. Or if the budget is an issue, REIs Quick UL ($99) has adequate cargo capacity for your needs (2,800 cubic inches) and a surprisingly good suspension for the money.
Hope the snow on the trails around here melts eventually. June-uary in the Pacific Northwest, indeed.
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