DD (15) likes Forever 21, Target, Altar'd State...and Amazon. A few things from both Macy's (primarily slightly nicer shorts to supplement the jean shorts from Target) and Kohl's. Think she likes the ability to search for very specific items on Amazon.
As with PP's - DD is only 4'11" and full grown - and even then some Forever 21 is skimpy on her but a lot is not. If she were taller a lot more would be 'not appropriate' in our house; she's busty so even she knows what's not gonna happen when coverage there is an issue. Their leggings last year were better than most stores, but it varies a lot year to year. (Better: had pockets, and 'interesting' designs/insets but still school appropriate for our house/school at least.)
If she likes dresses a number of online places like Lulu's are big hits, especially for dressier dresses.