...From what little I can see in the last panel, the Dashboard looks kind of crumpled...
...A Sudden crash?
Adding to that, John warned her not to take her seatbelt off... Meaning she took it off to turn around.
By the looks of it, she is being thrown out through the front of the car, and John was likely killed instantly... Damn, that is traumatic for the Protagonists... Or at least, the male of the two siblings.
...From what little I can see in the last panel, the Dashboard looks kind of crumpled... ...A Sudde
From the visual outside of the front window in the second to last panel, it looks like tree branches. But it looks a little weird to me. Maybe it's a fallen tree they crashed into? In which case, she probably doesn't get thrown far (if at all)...
From the visual outside of the front window in the second to last panel, it looks like tree branches