do you think this pack would be suitable for a teenager roaming Europe? She is 5'5" and only 115 pounds, average strength. I am wondering how heavy and large a pack she could manage.

A lot depends on how much weight is loaded into the pack, what the primary activities will be, and the amount of gear that will be necessary. People of average strength can usually haul around quite a bit more weight than they might realize, but of course the more weight means less comfort. Weight and size should not be an issue with this pack if the load is carefully planned. This pack is probably a decent choice (again, it depends on the activities) and will fit a torso of 14in - 22in, which should be fine, though measure her torso to make sure. The detachable pack works as a carry-on when checking the main pack or for day trips where the full pack isn't needed. This pack is also a top loader with a front access pocket, which is convenient when needing to get to your gear (important). The pack is well padded, adjustable and fairly well made. If you decide on this pack, make sure she tests it thoroughly. *Any* bad spots or sore areas that cannot be corrected through adjustment of the pack means the pack needs to go back (this is pretty rare). A little discomfort over a few hours will become a serious burden over several weeks. Good news is, BC has a great satisfaction/return policy, so it's basically a worry-free purchase.