I think it was meant to finish her character's growth arc - she went from a girl who tried to kill herself to someone who stood up for herself & her friends - by helping Noah escape, by helping Dawn fend off the bad cop, and finally, over-confidently, stabbing Dawn to help free Noah again.
All signs pointed to Carol, but I like Carol a lot more than Beth & Carol's character still has a lot of unresolved issues. Like with Bob, he found a group, found Sasha, and found happiness again. But with Carol, that book on childhood abuse dropped out of her bag before she got hit & taken to the hospital, so she obviously still has some stuff to overcome. Plus, she's a super-central character to the show, back when her husband was beating her & when she lost her daughter. Man, that episode where her daughter came out of the barn as a zombie really got me