The second Lois had asked her if she knew Clarks secret all along was when Kara had gone right to her cousins room. What Lois was probably thinking was meteor freak, because that made the most sense. She had a pretty good guess that Clark would be more than a little worried. And sure enough, she'd spent the past few minutes trying to figure things out and calm him down. This was his secret to tell, but it affected her too. He wasn't the only Kryptonian walking around the city. She wasn't that worried. But she also knew Lois had feelings for Clark, and she was pretty sure Clark had them for her. Not that she was going to bring this up. But because of that, this couldn't explode into disaster.
When Lois banged on the door, Kara glanced to Clark before walking at a human pace toward it, turning the lock and opening it slowly. At first it was just her looking out the crack of the door to Lois.
Yeah, she looked pissed.
Silently, she stepped back, giving room Lois to push open the door and enter. Though while she did that she would be positioning herself beside Clark. She considered Lois to be one of her best friends, but she'd do just about anything to keep Clark safe.