most of mine are from the 90s and very early 2000s (best period for teen/high school movies in my opinion) Clueless cruel intentions she's the man the craft 10 things i hate about you Jawbreaker (very similar to mean girls and easy A in style) Sugar and Spice
can't hardly wait - is a classic in the vain of the others but not really told from a female perspective but rather the perspective of various people in the film (male and female)
basically teen-romance-comedy films, haven't seen anyone posted these: Wish Upon a Star Vampire Academy Sugar & Spice Perfect Score Confessions of a Teenage Drama Queen Freaky Friday It's a Boy Girl Thing House Bunny Hot Chick 17 Again
No one has mentioned Wild Child. I vaguely remember it, but it's about a girl who is sent to a girls' boarding school and learns all these life lessons and goes through friendship drama etc. Kinda predictable but it's good for understanding how girls act towards each other a lot of the time.
"The House Bunny" with Anna Faris and Emma Stone "What's Your Number?" with Anna Faris "Not Another Teen Movie" an excellent parody film of teen movies "D. E. B. S." excellent campy movie. Sara Foster and Jordana Brewster "The Ugly Truth" with Katherine Heigl. Vibrating panty scene is great.