This sire bond isn't real at all.
Why Caroline and Vicki didn't had any problems? Caroline tortured Damon a bit(hitting him with every ウォール possible) and Vicki almost killed Elena, and others(which C'mon would happen if there was a sire bond), and both were turned によって Damon's blood. And I think there are many others examples that we can use. Again I repeat, this is first time in the show, and many people were turned there, when "there's" a vampire sire bond. Another example can be Jenna, which was turned によって Klaus, and there was no sire bond, because Jenna fought against Klaus.
Pure and Simple, becoming a vampire, everything Elena felt for Damon went bigger. And because the Stelena broke-up almost existed since Stefan left in S2-S3, the feelings for Stefan couldn't grow up as much as the feeling for Damon did.
IT DOESN'T EXIST AT ALL. I repeat no sire bond.