So I was playing through the game again to try a different path, and noticed a line MC's thoughts had about Bella's "marriage" and how if he knew "back then" what was really going on, he would have stopped her, or made a cry for help. I'm guessing Based on her reaction to spending the night with MC in his room, and how she loathes adulterers more than anything (which she says she became herself by sleeping with him), that her husband cheated on her and left her a long time ago, but because of some mental illness or refusal to let go, still holds onto the ring and hides something about him in the room that she keeps locked, and acts like they're still married. (she even at one point early on, in her head, begs her husband to hurry up and come home.)