Slightly heavy at ~3 lbs, but both the Lowe Alpine Nanon and the Gregory Jade 50 could be good options. I have found that Gregory women's packs fit better than Osprey women's packs, and are overall a better value. I haven't used the Nanon personally, but it's a nice simple pack and I've met several women who carry it and like it.
I carried a Gregory women's pack for a number of years before switching to a Mountain Laurel Designs Prophet. I think both the Prophet and the Arc are incredibly comfortable packs. Strap placement, hip belt, torso length, everything about it feels almost custom made for me. For reference, I'm 5'5" and 115# and reliably wear a short torso/small waistbelt. I know you mentioned frameless, but the MLD packs were comfortable enough to convert me (that, and a sub-10lb baseweight).
I "test drove" a GG Crown VC Ki not too long ago and I am pretty in love with it. Super cushy after several years with my MLD pack, but I think it will be the perfect pack for winter trips and casual trips where I'm carrying 6-packs, Tolstoy novels, etc...
As has been said many times before, go to a good gear shop if you can and have her try on lots of packs, with weights in them, and walk around until she gets a feel for what works and what doesn't.