Roy, IMO the internal frame is a good feature for a Backpack. As the others have indicated, it tends to maintain the shape of the pack somewhat, especially when it's lightly loaded. The two aluminum bars don't seem to add a lot of weight.
When buying ANY Backpack, it's very important be properly fitted according to torso length. Most of the weight should rest on the hips, not the shoulders. Most quality Backpacks provide "load leveler" straps to allow the user to adjust the weight betweeen the shoulders and hips.
Two other valuable features that I feel are important are a detachable Daypack (good to use for carry on) and a "stowable" harness system to allow the straps to be stowed behind a zippered panel during air travel (so that airport conveyor systems don't tear them off!). I also tend to prefer a panel-laod pack (with zippers) as opposed to a top-load Pack (usually a drawstring at the top, which can't be locked).
You might have a look at the Eagle Creek line. They're extremely well made, have various sizes and are provided with a good warranty. They have some models specifically designed for women, however I'd recommend that your daughter try all models as some women find that the men's model fits them better.
I had a reminder recently on how important it is to be properly fitted. While waiting for a train in Austria, I left my Eagle Creek Backpack (40-50 lbs?) on for 1 to 1.5 hours continuously and hardly noticed it.
Hope this helps. Good luck and happy travels!