When you randomly appeared in a fight and used your skills to help the Titans they were all amazed, well accept Dick. Everyone voted for you to join the Titans since you're very skilled, Dick isn't agreeing with that, but since it's one against the rest they win and you join

While you were training you notice Dick is glaring at you and muttering things that sounds like he's total against you, for some reason "Can't believe that they let some random girl join our team" he scowled