He starts out small.
"I know your secret." A note, left in Whitney, Queen Mean Girl of School's, locker - just a scrap of paper, really, written in the loopy, playful cursive endemic to teen and tween girls the world over.
"I know what you've been doing." With a little heart, stuck in the cover of her English book.
...He watches, carefully, from the sidelines. Hoping to see paranoia growing.
"I've read your burn book." A colorful little flame pattern, in glitter-pen ink, folded and left on the desk that SHE always claims in Science class.
"You think you're good at NOSE-ing around, but there's a MOLE on the inside..." cute, squiggly underlines for emphasis, somehow slipped inside her lunch bag.
Meanwhile, little notes have also been passed to a select few around the school. The boy who she "rescued" from the bullies. The girl that had been mocked for having a training bra and then soothed by Whitney - just in time to share coveted Boyz B Boyz concert tickets that she'd gotten for her birthday.
The jock who was kicked off the football team after someone spilled that he'd plagarized his essay... after turning Whitney down for a date. And a few others...
Even Brittney, her Number 2 Bitch, may be casting odd looks at her idol, after getting a hot tip that Whitney may have been the one to leak that story about the time she wet the bed at a middle-school slumber party...
Each note carefully points attention towards Whitney being not quite the sweet princess she attempts to come off as... aiming to build up her paranoia, while at the same time, turning her allies against her.
Pointedly, he does NOT mention Siv, or give her any notice. After all, Whitney hadn't actually acted on her nasty plot yet... and any tie to Siv may lead back to the source...