The sister sleeping in the room is a classic "forced proximity" device used to create tension, intimate dialogue, or a "protective" character moment.
"Hey... you still up? I can't sleep. The house is too quiet. Mind if I just hang out here? I won't get in the way." II. The "Fixing" Process Sensory Details: Focus on the sounds of your work.
When that person is perceived as sexually confident or flirtatious, the stress multiplies tenfold.
she woke up for snacks. ate my leftover noodles. called you "cute in a pathetic way."