It's more than I'd want to carry in a frameless pack, but that's just me - I never found them comfortable with more than about 15 pounds, and use a framed pack (Atmos 50) for my 20 pound load. I hike with one guy who easily carries 30 pounds with ease.

She's just going to have load it up, including water, and go hike an hour or two with it on, and not just on sidewalks: take it up a few hills, too. "Experts" will have well-informed opinions about what should work and why - but she's the one who ultimately has to carry the pack.