Rebekah realizes they're missing a brother a day before their house is to be filled with three Mystic Falls residents. She realizes that he's with Elena when she hears the nurse open the door to Elena's room.
She decides to wait until after dinner. If Elijah isn't out by then, she'll get him out and make him drink some blood.
She tells the other residents of the house not to disturb them, although she walks in on Klaus painting Caroline to do so.
If Caroline was human, she would have flushed scarlet at Rebekah's remark that she really didn't care that Caroline was sitting for a portrait, just as long as she didn't walk in on her brother drawing her like one of his French girls.
It takes Caroline thirty minutes to recognize the Titanic reference and to recognize that Klaus was not drawing French girls. At least not this century.
Rebekah worries slightly for Elena and Elijah. He's in love with her and she's in a coma. The coma Elena's in can't be easy either. She always wondered what had changed, what she had lost when she was undaggered again. Elena is aware of the world, of the people visiting and what they tell her. That might be even harder. All of the people coming to visit in a day will be dead within a century. Elena is young, and she can't imagine having that fate. But she remembers she was already a vampire when she was Elena's age. All perspective, she supposes.
They're all trying to give Elena and Elijah space, and Rebekah tells Kol that she will won't be on Elena and Elijah's relationship. At least not until Elena's awake and in the world of the living again. Then she'll give her grief like she gives Caroline.