Actually Caroline wanted to snap his neck so they had one less thing to deal with and he was threatening Stefan already and she wanted to stand for him. When “Tyler” flipped out his werewolf side it startled her. Then Stefan stepped in as he always does because he feared “Tyler” was going to hurt her. I believe she was trying to help Stefan.
I can see that she that maybe will go through some guilt afterwards because she might think she’s the reason Stefan died.