It's simply, Caroline said "I did a wrong thing", and is obvious that this wrong thing is have sex with "the enemy" I have to thoughts:
1) Caroline will tell Elena, with Elena controle herself, and Elena will get mad, and they will have a fight. (The rest part of the especulation is the same for both of the theories)
2) Caroline will tell Elena (with Katherine in her) about the adventure between Klaus and her. Elena will act like nothing happen, and Caroline maybe start to didn't recognize her friend Elena. Bonnie, Stefan and Damon will know it too, and I think that she will get mad, and shout to Care. Stefan will judge her, but maybe exist a conversation between this two friends, and Stefan wil understand (because he slept with the enemy too, Katherine). And finally Damon, I think he will laugh. Because Caroline always attack him because Delena, and finally she did a wrong thing "like Elena being with Damon". I think also Matt know that, or suspect. Because, Rebekah appeared to save him. Matt didn't know that she have sex with the hybrid, but I'm sure that he know that Care had being with Klaus. But when the quarterback will figure this out, he will get mad, because he hate Klaus. And Tyler, when he will know everything about it, will be angry and violent.
Anyway, Caroline will have a fight with everyone (Stefan/Elena/Matt and Bonnie, because everyone did a wrong thing once, and she supported them, and know they argue with her. Stefan slept with Katherine, Elena with Damon and Matt with Rebekah. And Bonnie forgot the fact that Jeremy cheats her with Anna, the ghost)
Finally, Caroline will run away and her heart will want being in New Orleans with Klaus, the only person who love her and never judge her.
I think that the next crossover between Klaroline and both series, will be Caroline in the Originals, because Klaus promised never come back.