I think that door is important, really, really wonder what Bella hides behind it, why she reacts the way she does when the MC knock on it, also when MC tells Jill about it, and Jill becomes skeptical about the door... to re-use what you said, could be James kept in a coma, could also be his corpse she keeps there, for all we know.
I wouldn't be surprised if Bella was akin to Leah in BaDIK, not in the sense she'll try to kill people, but in the crazy sense. And to be sure, I don't care that DPC said there wouldn't be a Leah in BaDIK, he can say what he want, doesn't mean it's set in stone, that scene is dark for a reason, the last 4 lines especially.