Negan Killed Abraham and Glenn in one of the bloodiest episodes of the series. Although Abraham was in a relationship with Rosita, he finally ended the relationship after falling in love with Sasha. However, their love life was short-lived because Abraham was killed soon after. Sasha was very angry at Negan, and she was looking to avenge the death of Abraham. Initially, Sasha and Rosita were not on good terms but eventually agreed to go to the Sanctuary and kill Negan.
Sasha and Rosita arrived at the Sanctuary and waited for Negan to show up. The plan was to use a sniper rifle because Sasha was a good shot. When Negan showed up, Sasha could not take the shot, and they agreed to enter the compound and kill Negan at close range. Sasha had already decided that she better die trying to kill Negan. Ergo, she tricked Rosita, locked her outside the fence, and decided to kill Negan alone. However, she was captured and locked in a room.
The following day, Negan came to talk to Sasha, trying to understand her motive and why she was so angry. However, he found David trying to rape Sasha. Angered by the behavior, Negan killed David and gave Sasha a few choices, including trying to kill him (Negan), killing herself, or joining the Saviors. Eugene requested to see Sasha because they were friends in the past. He was granted permission, and he tried convincing Sasha to join Negan instead of dying. However, Sasha requested Eugene to help her one final time because they were friends. Eugene obliged.
Eugene had crafted a poison pill to help one of the women sleeping with Negan. However, he gave it to Sasha to end her life painlessly. As they were heading to Alexandria, Sasha requested to travel in a coffin because she wanted to be comfortable and alone. She took the pill, and upon reaching the gates of Alexandria, Sasha had died and turned. When Negan opened the coffin, she attacked him only to be rescued by one of his men. When Negan asked, Eugene suggested that Sasha could have died from lack of air/suffocation. However, we all know that Sasha died from a suicide or poison pill.