My theory about Bella:
- Isabella's husband is in the army. I think that is kind of an agreement now. There are clues about it
- The couple had problems because he was often away from home (quite common in military families, sadly). The moments he was at home on leave, he used to try to compensate his absences with situations like the one of the surprise visit to Bella's job trying to be sexy and romantic, but it didn't work. Bella was cold with him and it was even worse.
- Bella feels alone and becomes closer and closer to Jill. I don't know how they met each other, but maybe she's related with Bella's husband, or Bella is somehow related with the Royce. At some point, Jill "makes a move" on Bella because she feels scared and ansious about sex and wants to "experiment" it in a safe environment with someone that she totally trust, but it goes wrong. Maybe James knows about it and it's another source of conflict between Bella and him.
- At some point, Bella's marriage was totally rotten and there were continuous fights for any reason. Bella's husband was going to be deployed again and he wanted to spend the last Christmas in family before going overseas, but there was another fight during the family dinner, and in anger, James thrown the table to the floor, grabbed his duffel bag and gear from the back room, where he kept it, and went to spend the night to the headquarters. Then he left to Afghanistan or any other war zone and the couple didn't even say goodbye.
- Bella's husband was declared Missing In Action. It's been 3 years, nobody knows for sure if he's alive or not but most people thinks that, after all that time, he's dead. Bella continues wearing the ring and behaving like a married woman, but doesn't even know if she's actually a widow.
- Now MC is a friend and visits her regularly, so she carried some of James's belongings to the famous room and closes the door, but not all of them, only the ones that could MC make questions about things she's not prepared to talk about with other that Jill, who knows the whole story. For example, maybe James got the African mask in one of his deployments overseas.
- At some point (after or before James's departure, doesn't matter), Bella lost her job. She was alone and with nothing to do all day long except feel depressed and guilty at home. She wasn't even capable of looking at James' photos, so they are face down, but she doesn't dare to just put them away in a drawer because it would feel like if she would have given up in James. Jill is a Royce, so she helped her to get the job in B&R. That's the main reason why Jill is so important for Bella. They are even closer now that Bella is alone.
- If Bella and MC are a couple, she feels guilty, not only because MC is his student, but also because she doesn't even know if she's cheating her husband or not. But she knows that she can't continue living like the last 3 years. She has made up her mind and she thinks that knowing all the story and drama, Jill should be more supportive. But Bella can't actually get angry with her, because she owes her too much, so she only reproaches her this:
I don't know if this is what DPC has in mind about Isabella, but I think is a decent theory. Is coherent, explains everything (I think) and is not too far fetched.