She comes to check on him, because it's what she always does. It's part of the job, as much as anything else Anna does daily. She checks the perimeter fence, helps ration the food, goes out to clear new zones, tries to make a life for them here. And after all that, she checks on Castiel. She does it because she has to, but whether its because of deep set guilt she can't quite get over, or just because a small part of her still cares is anyone's guess.

It means that she's close enough to hear that bitter, broken laugh, and it turns out Anna still does have some shreds of humanity left in her because that sound hits her like a punch to the stomach. Knocking softly on the door, she doesn't wait for a response before letting herself in. There's no point, it's not like she'd listen if he protested anyway. She's trying to smile when she heads inside, but Anna knows as well as anyone that she's not fooling anyone.

"Did I miss the joke?"