The reader-character (often a self-insert or named OC) has to make room. This is where the physicality of sleeping is described. Do you give her the bed? Do you build a blanket fort? The most popular “full” AUs use the —you both lie on the carpet, staring at the ceiling, because beds feel too vulnerable.
The problem is your apartment has exactly one bed. The couch is a two-foot-wide IKEA disaster that even your cat refuses to sleep on. You tell her you’ll take the floor, but Ellie just laughs—that tired, scratchy laugh she’s had since she was twelve—and kicks off her boots. ellie idol sister sleeps in your room while au full