Caroline doesn't have to know everything. Benefit of Bela keeping her mouth shut. Also, benefit of Bela not being around all that often. At the same time, Bela knows that Caroline could forgive him eventually. He bit her once, and if she forgave that then she could forgive this.

But Bela doesn't actually consider things in a normal way, so it's probably more the first two.

"Must be nice. To have a life to go back to."