Sometimes I think I'm watching a different show than some other folks...
Carol ran in front of the car on purpose. They saw the car coming from inside, they knew it would get there and it was a race, and she knew they wouldn't make it. She ran in front of the car to save Daryl - the entire episode is designed to show you how Carol has turned into a person of action. She makes decisions quickly and acts on them, from what she did at the prison, to what she did with the girls, to what she did at Terminus. She made decisions about what she felt had to be done to save others, and she acted on those decisions without consulting or asking permission. She did the exact same thing here - she saw the car coming, knew Daryl and Noah weren't going to make it out, and sacrificed herself for their benefit. It's not quite what we had expected, i.e. she's undercover, but this also works within the character they've created with her, and expectations about her behavior.
At least that's how I saw it.
And yes, the fires mattered - ignoring the obvious title of the episode, Carol even says that each person she becomes gets burned off.