Yeah I also think Sally's been involved in Magnar's machinations, I mean, she kinda says something that could be interepreted as a hint to the fact that she's been duped/manipulated by Magnar to a certain degree, so I wouldn't be surprised if she's revealed as the one that hacked the laptop or the one that placed the cameras.I also believe she is overly nasty with the MC because of guilty. She is feeling guilty, completely guilty. Magnar and the nerds wants to make the other Frats pay and who do you think can enter the DIK's parties to acess their PC? No nerd but Karen and Sally were invited to DIKs parties.
So it's either Sally or Karen and I believe it was Sally, which is why she is having trouble with Magnar and is buying more meds from Quinn and is having trouble with her studies and is getting more and more nasty and guilty over time.
At least that would be my theory, maybe someone else is working through or with Magnar. And I shudder at the thought of Magnar actually pimping out Sally to try and get an opening to the DIKs... like, someone was fucking Rusty in his room in the night Cathy's cluck got posted.