You’re not a trained therapist so don’t even try to de-ice her. Instead just accept the fact that your roomie and you are not going to be BFFs. And if the meanness gets worse for what seems like no reason, ask her what’s up. Maybe she has a family situation at home she’s upset about or maybe she’s annoyed that your alarm clock ringtone is the soundtrack from Grease. You won’t know if you don’t ask.