I keep waiting for the show to go there as I think that it would make for a really interesting scene if Caroline did ever confront Elena over doesn't it bother her how Damon treated her friend in the past, and at one point I did believe that the show was going there eventually as Caroline's reactions to Delena just keep on getting more vocal, so it did seem like the writers were building up to making a point. But then interviews lately have made me wonder if they're just going to sidestep the whole thing, give in to audience response, and have Caroline apologise to Elena and acknowledge that she also slept with a bad guy like Klaus

And I think that Caroline's attitude changed in season 3 after Elena confessed that she kissed Damon in the season 2 finale. I would say that she tolerated Damon before that, and even now she doesn't really say much to Damon himself, it's just when she's around Elena that she's so repulsed by the idea of Elena actually dating Damon or being attracted to him, and I do think that must be a subconscious reaction to thinking of Damon as boyfriend material and how he treats women that he's dating. The writers could tone it down a bit with 'Stefan is your epic love' definitely lol as that only makes it appear that Caroline is all about the love triangle, but I've just always figured that there must be more deep-rooted issues there for Caroline to spend the last three seasons shuddering at the thought of her friend dating Damon and never letting that go, even when the writers know how much that's making some of the audience turn against her and call her a hypocrite for favouring Stefan