Because she didn't go back to kick-ass Carol once she escaped.
As soon as she broke Maggie free, Carol just wanted to leave and NOT kill the captors and it was Maggie who said 'no, we have to finish it.' That was totally, totally un-Carol like.
Carol is usually just of the notion they have to die.
It was Maggie slitting throats and bashing brains in and killing people, while Carol stood behind and watched on.
She then, when confronted by her main captor, said 'just run!' When normally she would have just pulled the trigger without even the blink of an eye.
Maggie was urging Carol to shoot, and kept saying 'shoot her' but Carol was all hesitant and Carol never hesitates! She had tears in her eyes the whole time.
Carol then had a second chance to shoot the leader, but again said 'run!' She went right up to her with the gun and couldn't pull the trigger and the Saviour was able to attack her, even though Carol had the gun pointed right at her face from about a yard away.
Carol was then in tears when the woman was impaled and struggled to speak on the two way radio.
She then said she should have killed the one in the woods and was upset about that, again very un-Carol like and normally she wouldn't have missed.
She then saw the 2 Saviours burn on the kill floor and again looked visibly upset, again not normal Carol.
Then as the walked past the zombies, it was Maggie who was killing them all and Carol stood behind and just watched and didn't help.
When Carol and Maggie open the door to be confronted by Glen and some of Rick's team, Carol is then asked if she is okay and again she is visibly upset and answers 'no!'
You can see into her eyes and she is really upset and distraught. So not like normal Carol who is so hard nosed about these things.
Rick then shoots the last Saviour and Carol yet again seems very upset and shaken. There's a real close up on her face that lingers and you can see in her eyes that the whole thing has had a profound effect on her.
Just wasn't the same Carol as before.