In Chapter 5, what happens in the attic between Lissa and Christian?

Lissa tries to leave the attic when she sees Christian, but he stops her. Christian tells Lissa that he has been using the attic as a place to get away from everyone. Christian guesses that Lissa had to feed on Rose while they were in hiding, but promises not to tell. Christian tells Lissa that she can stay in the attic for a while if she wants, and he heats the air for her using his fire magic.