Blaire Lily

Blaire Lilly is the main protagonist, but arguably the true main antagonist of the 2015 film Unfriended. She was a friend of Laura Barns, but was the one who posted a video of her which drove Laura to suicide, and during the film allows two of her friends to take the fall for her. Throughout the film, she plays the typical "final girl" roll, but when she's the last one alive, the truth is revealed. She is played by Shelly Henning.

Background
Blaire Lily, was a childhood friend and best friend of Laura Barns. Blaire knew that Laura had a troubled relationship with her uncle and it was assumed that he sexually abused her. Though they were best friends, Laura was known to be a bully by her classmates and she even admitted herself that she was a bully.

One night after being intoxicated at a party, Laura suddenly passed out and was covered with feces, which was secretly filmed by an unknown cameraman, later revealed to be Blaire herself. The video was then uploaded onto YouTube without her consent, which made Laura a victim of cyberbullying and humiliation.

On April 12 2013, Laura had enough of the cyberbullying and decided to commit suicide in a public area by shooting herself. Her suicide deeply affected everyone who knew her and witnessed it and her Facebook account became a memorial and dedication page. However, little did they know that the vengeful spirit of Laura Barns still haunts this world after she accessed a mysterious Skype account called Billie227, which she used to exact her revenge by killing those who didn't confess about posting the embarrassing video on YouTube

Unfriended
The film takes place in a pseudo "found footage" format of a group of friend communicating over the internet, specifically Skype. Blaire is contacted over Skype by her boyfriend Mitch Roussel and later joined by three of their friends: Jess Felton, Ken Smith, and Adam Sewell, as well as a faceless account named Billie227, who claims to be Laura.

The group make several unsuccessful attempts to get rid of the user. Later they suspect that another girl, Val Rommel is simply pranking them. When she is invited to the chat, Jess's Facebook is suddenly updated with photos of Val drinking and smoking at a party. Jess, who proclaims her innocence, attempts to delete the photos, but they continue to reappear. After finally deleting them, the photos are mysteriously posted by Adam's account. After being threatened multiple times by Laura, Val eventually calls 911 to report online abuse and signs off.

Laura e-mails Blaire a link to an Instagram photo of a message Laura sent Val a year earlier, begging her to remove the embarrassing video. Val refuses and tells Laura to kill herself. When multiple Instagram users criticize Val, she is brought back into the chat suddenly. Val is seen silently standing motionless in her bathroom, next to an open bottle of bleach. Blaire calls Val to check on her. The police arrive and shout out police codes. The group try to work out what happened to Val using those codes, and her death is eventually labeled a suicide.

When Laura kills Ken, she forces them into a game of Never Have I Ever, threatening to end the loser's life. Through this game, she reveals dark secrets that put the friends at odds with each other. Adam becomes enraged and uses the game to force Blaire to reveal that she is no longer a virgin, having had sex with him twice. Mitch retaliates by forcing Adam to reveal that he gave a girl roofies at a party, had sex with her while she was unconscious and then forced her to get an abortion when he found out that she was pregnant. Blaire and Adam then receive messages from their printer, but refuse to reveal what their messages say. Mitch, angry that Blaire and Adam are apparently sending "secret messages", threatens to log off, to which Laura responds that if he does, he will die. Eventually, Blaire shows her note: "If you reveal this note, Adam will die." Adam immediately shoots himself in the face as his screen shows his note: "If you reveal this note, Blaire will die".

Laura then demands to know who uploaded the video of her. After Laura privately messages Blaire on Facebook, asking who posted the video, Blaire lies that it was Mitch who uploaded it. Mitch suddenly dies when he stabs himself in the eye, leaving Blaire alone in the chat room. As Blaire breaks down crying, Laura thanks her for her help, but tells her that she must confess to one more thing. Blaire tries to placate Laura by showing her past photos of when the two were friends. Laura uploads the humiliating video of her on Blaire's Facebook account, but in this version, Blaire is revealed to be the cameraman. The video is flooded with hate comments blaming Blaire for Laura's death. Blaire, in a state of shock, sits silently just as billie227 signs off followed by her bedroom door creaking open. Silhouetted hands appear out of nowhere and they suddenly close Blaire's laptop (as the film switches to a first-person view). Laura's vengeful ghost suddenly appears as Blaire unleashes one final scream

Trivia

 * Blaire is similar to Jill Roberts from Scream 4
 * Both fit the "Final Girl" criteria, but it is later revealed to be a façade.
 * Both seem humble but are really cunning and manipulative.
 * Both are in something of a love triangle, and are responsible for the deaths of both lovers. While Jill directly kills hers, Blaire throws hers under the bus to protect herself.
 * Her betrayal of Laura takes a harder light to it when it turns out Blaire was such a close friend that Laura had confided in her about her uncles abuse. This means that despite Laura trusting Blaire, and Blaire still betrayed her in the worst way possible.