I mean, the one roommate heard a voice she didn't recognize and then saw BK walk past her and then in the kitchen. Um, you saw an intruder and you didn't call the police? Make it make sense.
I can't make it make sense exactly but I will say I'm not terribly surprised the one roommate didn't call the cops after seeing an "intruder". When I was in college, I shared first a dorm room, then an apartment with "C". C was VERY popular, and after a while, I just grew used to seeing strangers in my dorm room or (more frequently) in my apartment. Fortunately, none of them turned out to be dangerous...and I would probably be a lot more suspicious if I was a young person in college now than I was back then.