Elijah still couldn't believe Klaus had undaggered him. Sure they had been partners all those years, but he assumed his brother was still angry with him for trying to stop him all that time ago with Katerina. Elijah was of course still planning on stopping his brother, but he wasn't advertising that fact. He was going to be a little smarter about it this time, because he knew that Klaus was even more a handful when he was vengeful about something.
Elijah had showed up at the dance that night, hoping he would find Elena. She needed to know what she was really getting herself into, and if he had to the one to be honest with her he would. He hadn't learned the truth about his brother walking around in the body of another man, but he did know of Klaus' witches, and he was sure he could handle himself against them. He had survived this long after all.
And if he did run into Klaus he could always say he was there to help him. Elijah may be a noble man, but he was better at lying than most people realized. For the moment he was fading into the background of the dance, but then he spotted her dancing with the teacher. There was something off about the man, but Elijah would have to get close to discover the truth. So, for the moment he waited, quietly watching the crowd to see if he could Elena on her own.