yeah another good point... but than i dont know what the starting scene in ep8 is for. This very scene has to mean something important... and that Bella is running away from that library too...I still firmly believe that James and Bella split up due to the loss of a child and the strain it put on their relationship. I feel like that's what's behind that locked door. Her childs bedroom that she's keeping as it was when the child died. The only evidence I have that supports this theory is the step stool in the bathroom next to the sink...unless James was a midget, I don't see any other reason that should be there.
but ok, yeah a childloss could fit too. Maybe she lost a child with james, James has left after that. Bella went crazy about it, began to hallucinate, the boss noticed something is off with her cause she was hallucinating her husband and send her home... than she lost the job and started a new one at B&R. And nobody knows about all of that... only the boss at the library, and thats why Bella runs away from it at the date with the MC.
But anywas, the shizo-theory is the best in my book, and it doesnt really matter what is behind the locked door... childloss would of course be the hardest scenario i can imagine for now...