Vivian Darkbloom

Vivian Darkbloom is the alter ego of Alison DiLaurentis in Pretty Little Liars.

Biography
After Caleb begins hacking "A's" phone, the girl's discover that Alison had created an alter ego, after she too was being victimized by "A." Alison told Hanna she was tired of being herself so she created a new identity. She also spied on "A" as Vivian Darkbloom.

Although, It is possible that Vivian Darkbloom can be the twin and all the times that "Alison" was shown as Vivian was never really Alison, but The twin all along. The twin was probably just named Vivian to throw the audience off.

Season 2
A Kiss Before Lying

Vivian is first introduced when Caleb hacked the video to see her photo license. Hanna then remembers that she once saw Alison with dark hair in a hair salon. She recognized her voice and was surprised to see her with a wig, but Alison told her that it´s just her hobby - pretending to be someone else.

UnmAsked

Aria and Spencer discovered that the day Alison disappeared, Vivian stayed in the Lost Woods Resort. Mona later remember that she saw Alison/Vivian in a shop in Brookhaven spying on someone, asked her who she was spying on, to which Alison told her to play along to the idea that they did not know each other. With Mona's unwavering desire to become another "Queen Bee", she kept Ali's secret, to which she received a card with phone number in return.

Season 3
It Happened 'That Night'

When Hanna visits Mona at Radley, Mona is seen smiling at empty chair (assumed to be empty for Hanna). This is where Mona sees Vivian reading Lolita.

 A DAngerous GAme 

In A DAngerous GAme, Alison was revealed to be Red Coat, which means that Alison has/had 3 identities. Alison was seen with the Red Coat on, but the difference with Vivian's and Red Coat's coat Vivian's has no hood while Red Coat's coat has a hood.

Appearances(3)
Season 2(2) Season 3(2)
 * A Kiss Before Lying
 * UnmAsked
 * It Happened 'That Night'
 * A DAngerous GAme