Janice's frenemy with bad makeup from Why Not Janice is a materialistic, insulting, condescending and patronizing entity who comes into Janice's life to incarnate the percfect strawwoman. She seems, however, perfectly aware of it. In a Q&A, Janice stated that she had a cringe-worthy experience in school, so this may have inspired this character.
Sooni from Tales of MU both uses and subverts this trope. While she starts out appearing to be a textbook Alpha Bitch, it quickly becomes clear that she's trying to live out a fantasy, with a Girl Posse made up of virtual slaves and little actual popularity.
Survival of the Fittest is a roleplay that focuses on high school students. So, it's not surprising that at least one pops up every version:
Aphrodite, though somewhat subverted in that she has no Girl Posse and is excluded from the other Olympian cliques.
Hera is a straight example, being the queen of the gods and having her Girl Posse of Demeter and Hestia. Also she often puts down other gods and goddesses. She also often suffers humiliations due to her husband's chronic infidelities and having to put up with his bastard children on a daily basis.
Solange (Tansy Walcutt) of the Whateley Universe, complete with a perfect body, blonde hair, a girl posse, and sycophants. Worked her way up to queen of the Alphas at Whateley Academy before her downfall.
Ami in Sailor Nothing is one. She eventually pays dearly for it, becoming an instant Woobie in a single scene that's so horrific it makes the protagonists feel guilty for hating her. Aki is a subversion: she's pretty, popular and head of the Fashion Club, but she is (secretly) friends with the class weirdo and feels trapped by the superficiality of her life. After she's publicly humiliated and dethroned, she realizes it's the best thing that ever happened to her and turns out to be a pretty nice person.
Kelly from The Crazy Kids of Grade 5 is rich, spoiled, and thinks she is the leader of the 5th grade popular group.
Emma Barnes in Worm leads a trio of popular girls at Winslow High in an extended bullying campaign against the protagonist, Taylor Hebert.
Porkchop 'n Flatscreen! gives us Mina Kim, who bullies other students with the aid of her posse, the Bangers. note The name comes from the fact they all have identical haircuts in the front - bangs. Later episodes reveal there is more to her than just that (although it doesn't change her basic nature).
Sonya in Prolecto starts out as this. Then she becomes a succubus, and realizes that she finally looks like the monster she always was...and BREAKS.
Teela Tether from No Boys Dorm is this. Supposedly the richest and most powerful student at the Academy, she is determined to expose Lara No as not actually a student there. She enlists the Shadow Order, who carry out the wishes of the Academy's Elite students, to do so. She also asks a guy to the Academy Ball simply to stop him going with someone else, has the Shadow Order trash a girl's dorm room because her assignment was better written than Teela's, generally ruins really sweet moments, and- in the final episode of the season- actually tries to kill Lara with a garden rake.
In the animated short/student project The Colors of Evil, the main character, Vivian, is a goth girl bullied by a Valley Girl named Nancy who openly trash-talks her (even as Vivian is standing right next to her) and literally uses her as a doormat when getting off the bus. The plot of the short is Vivian summoning a demon for the purposes of trying to get revenge on her.