Ellie Landsberg

Ellie is the younger sister of Annie on Netflix's Maniac. (2018)

Throughout the show and the questionable trail, Annie must come to terms with her sister's unjust death and really say goodbye to her.

Death
Ellie dies in a car crash. She and Annie were not paying attention whilst driving, taking pictures in the car and do not see the truck in front of them. Annie was able to escape, Ellie wasn't and she did not survive. Annie later reveals in Episode 10, as she's come out of the program how she feels about her sister's death.

S1, E10 - Annie talking to her father - "Then your daughter died, and it was the wrong one. It was the easier one, who was good at life, who made you laugh, who didn't cause problems, who always called you, who didn't remind you of her mother."

The truck driver was referred to as Greg F.U.N Nazlund. He was stoned and had been driving for 30 hours, so wasn't paying attention to the road either.