Elena walked to Damon's room. Something was bothering him, and she knew it. What really irked her was that he wasn't inclined to share any of his feelings.
Elena wondered for a half a second if it had anything to do with her. It just didn't seem likely to her, so she wondered what else it could be.
The only other thing Elena thought it would be was Stefan staying in Mystic Falls, Virginia, in the same house she had taken up residence with Damon. She wondered why that it would irk him so much. She knew despite all the crap Damon had given Stefan over the hundred sixty plus years, he still loved his brother.
In that very moment, she knew it had to be Stefan, and something was bothering Damon about him. She just didn't know what it was about Stefan that bothered Damon.
Elena knew right then and there that she had to keep her eye out because if there was trouble coming, it normally came to her whether she was a vampire or not. She also decided that she was going to let Damon deal with his brother, and if he needed help, she was at his disposal. That's all she could do.