Which "friend" was the worst?
For me, it was Blaire. She filmed and posted a humiliating video of her childhood friend, who she knew was going through familial issues possibly related to molestation or rape by her uncle, and then she joins in on the online bullying under fake screen names that led to her suicide.
She shows the note that gets Adam killed.
On top of that, she cheated on him twice and lied about it being once and only when they were drunk.
Blaire seemed so innocent at the beginning, all making plans to lose her virginity to her high school love at prom and blah blah when really she was just a horrible person.
I only felt sorry for Jess. Yes, she also joined in on the bullying, but at least she didn't film or post the video and her only other crime was telling people Blaire had an eating disorder, which as far as high school gossip goes is pretty tame. Kids do worse than gossip about that petty crap in the hallways.