The squinty eyes really got me.
Poor Buffy going from a quiet 2 story house with a mother that worked all the time to sharing a small dorm room with someone like KATHY. The only thing that made Buffy no longer being an only child believable in S5 was that she is a nurturer.
Willow: Are you loving playing nurse maid?
Buffy: Oh yeah.
Dawn: Buffy said that she likes that you are all weak and kitteny.
Spike: I don't need you coddling me.
Buffy: I'm not. Now go to your closet!