Sarah’s death happens after Bear sneaks out to meet her while Nikki is asleep. Real Nikki briefly breaks through and begs Bear to kill her, making it clear she is trapped and suffering, but Bear leaves anyway.
In the car with Sarah, Bear lies about Nikki’s dad dying to explain Nikki’s behavior. Sarah is frustrated with Nikki and tells Bear that Nikki and Ian had been hooking up for two years. The conversation shifts into something more intimate, with Sarah shooting her shot, and then Wish Nikki appears.
Wish Nikki runs up to the car, breaks through the glass, and uses a brick to smash Sarah’s face against the steering wheel. Sarah’s death is graphic and prolonged, ending with a shot of her exposed eye peeking through the damage. Nikki apologizes while also blaming Bear, telling him that he wanted this.
You see the whole damn thing. All the smashing, the exposed eyeball. All of it.