Oh, maybe Diane Duane's Young Wizards series? Speaking of Trek tie-in novels...because she wrote some...
Anya ,'Touched'
Literary Buffistas 3: Don't Parse the Blurb, Dear.
There's more to life than watching Buffy the Vampire Slayer! No. Really, there is! Honestly! Here's a place for Buffistas to come and discuss what it is they're reading, their favorite authors and poets. "Geez. Crack a book sometime."
She might like James Dashner's Maze Runner series, or Robison Wells's Variant and Feedback.
I like Amy's recs and second both. I also like Starters by Lissa Pierce.
The Graveyard Book, as well as the other Gaiman books mentioned above. The Series of Unfortunate Events.
Definitely all the Tamora PIerce, but yeah, my first thought was "has she tried the Star Trek/Star Wars books?"
Skulduggery Pleasant, if she digs Harry Potter.
Percy Jackson is popular and fun.
I loved Christopher Pike at that age, for the creepy, supernatural-y when Stephen King was still beyond me.
She likes Harry Potter, The Hunger Games and The Omen. She loves musicals,video games, Star Wars/Star Trek and is impatient and easily bored.
For a kid who likes musicals, I'd recommend Better Nate Than Ever by Tim Federle, a fun new middle-grade novel about a kid who goes to Broadway, and Drama by Raina Telgemeier, a graphic novel about a middle-school drama club. Graphic novels in general might be something to look into, actually.
Diana Wynne Jones?