How old is your daughter, and how much does she weigh? (I'm assuming this isn't your 22-year-old daughter, and "school" isn't her senior year of college.) With kids, these are the important factors. Age, because that indicates how far along her bones and muscles are in forming. Even though she's semi-athletic, too much weight or too flimsy a suspension could cause lifelong problems if her bones aren't sufficiently formed to handle a 35 pound load.

Also, the general rule is that pack weight should not exceed a quarter to a third of the person's body weight (I'd modify that to "ideal" body weight - an out-of-shape 120 pound video gamer will not be able to carry more than a fit 100 pound person for an extended period. If your daughter is tall and fit (which it sounds like she is), then she would fit more toward the one-third end of the spectrum.

I'd be looking for a good suspension, not necessarily a light pack. Deuter and Osprey both make good youth packs with sturdy suspensions. Not sure off the top of my head whether they fit your budget or weight criteria. I'm not sure if youth packs come in 60+ liter capacities - but at 5'8", she may be able to use a female-specific adult pack. Deuter and Osprey both make such packs.

I've had only limited experience with youth packs - while I led youth groups, my hands were tied by whether parents chose to listen to the above advice. Many put Tommy in an adult pack, figuring he'd grow into it eventually and not wanting to buy him two packs. We compensated by keeping pack weights low.

I think Oregon Mouse and/or Wandering Daisy have better experience with youth packs, as they taught children and grandchildren to backpack. I hope they'll chime in; listen to them, if they do.