Ariel followed Blair into her room and held the door before it would close with fast reflexes when Blair, who she doesn't know if she still has any idea she's behind her, almost smashed the door right on her face. Ariel shut the door after they have both got in and went to meet Blair on her bed, mumbling some kind of indistinct words under her breath.
"Blair, I don't want to involve myself in this because I'm not really family, but I think what you said to Lauren down there was too harsh. You didn't have to act like that towards her when she's your brother's girlfriend and…." Blair didn't let Ariel finish and had to interrupt her. The girlfriend part is what annoyed her the most.