I can't help myself, I gotta weigh in on this one!
Bella does consider herself married. She tells the mc in episode 2:
Bella: "This didn't happen."
Bella: "You're still drunk."
mc: "Are you...sure?"
Bella: "Fuckface... I'm a married woman."
mc: "Oh..."
Bella: "Go to sleep."
mc: "(Damn...)"
But she also thinks it to herself shortly afterwards:
Bella: "(Why did he...?)"
Bella: "(I don't understand...)"
Bella: "(I feel so...so...dirty...)"
Bella: "(This is not what a married woman does...)"
So there's that; Bella considers herself a married woman. But it's complicated. If we continue her thoughts from the above scene:
Bella: "(I'm so sorry...)"
Bella: "(It just caught me completely off guard...)"
Bella: "(How long has it been since a man did this to me?)"
Bella: "(Three years?)"
Bella: "(No, that can't be right...)"
Bella: "(I haven't gotten an urge to touch myself...that's all...)"
Bella: "(Until tonight...)"
Three years? She hasn't done anything sexual for roughly three years? Where has her husband been for that time? Because of the Burke-looking soldier in the mc's alcohol fuelled stumble through Bella's house, there is some speculation that he's in the army, but a 3-year tour of duty is kinda not likely.
So there aren't any legit explanations that can innocently explain why he's been AWOL for three years.
In episode 3, when Bella is lashing out at students in the library, the cause for it is the sexual tension between her and the mc while at the same time she is helping to set him up with Jill. Her thoughts once again:
Bella: "(I can't lash out at students like that...)"
Bella: "(...)"
Bella: "(I did the right thing.)"
Bella: "(This was for Jill.)"
Bella: "(Married women don't fool around with young students.)"
Bella: "(...)"
Bella: "(They aren't intimate with friends either...)"
Bella: "(But that...that was different!)"
Bella: "(It doesn't matter... I've stopped it.)"
Bella: "(Please, James... Forgive me.)"
Bella: "(Please, just come home again...)"
Bella: "(It's been long enough now.)"
The first part she's talking about how she shouldn't be fooling around with the mc, but the second part, being intimate with friends, we don't know who she's talking about (but there's some speculation it's Jill based on their argument in bed when the mc's on the couch). Then she goes on to ask for James' forgiveness and for him to come home again (after 3 years as we've speculated above).
But then in episode 4 (if you stay at Bella's house), she has the following thoughts about the mc:
Bella: "(Why can't I stop thinking these dirty thoughts about him...?)"
Bella: "(All these words that I'd never dare tell him...)"
Bella: "(It's adultery...isn't it?)"
Bella: "(Can I just decide to move on?)"
Bella: "(What if James comes home?)"
Bella: "(Would he blame me if I did this?)"
Bella: "(After all this time?)"
Bella: "(I have forgiven him...)"
So she is aware that moving on is an option on the table, she's just found it difficult. On top of that, she forgives
him. So earlier she was asking for forgiveness (for the mc, or for something that happened long ago) and now she's saying she forgives her husband. What went down three years ago?
Then in episode 6, the mc confronts her feelings:
mc: "We both want it. We wouldn't be here right now if it wasn't so."
Bella: "Yes, but I feel ashamed for wanting it..."
mc: "Because of that ring on your finger?"
Bella: "Yes."
mc: "I get it..."
mc: "But correct me if I'm wrong..."
mc: "I've had the feeling he's not around anymore... Am I wrong?"
Bella: "No, it's...different today."
mc: "Then, if that's the case... I don't see why you should feel ashamed."
mc: "You should be allowed to feel something else."
Of course the mc is just a horny cunt trying to convince a girl to suck his dick, but he's not wrong. Her husband is gone, and has been gone for quite some time. Their marriage is over, but Bella is struggling to come to terms with it. How Bella's situation got to this point we don't know, she and her husband could have both been unfaithful, had a big fight, and he left but she didn't want it to end at the time. Or, he died, and she's struggling to accept it. Who knows.
Bella had no intention to start the relationship with the mc, she didn't file for divorce because she may have been holding out for her husbands return, or she used the marriage (and the ring) to keep men (particularly Burke) at a distance because she wasn't ready for another relationship.
None of this makes her a bad person, and if your husband leaves you and three years later you start to have feelings for someone else. I don't believe that's cheating.
By the end of episode 7, if the mc is with her, she removes her ring. She decides it's time to move on. At some time she should probably legally get a divorce if it's required (assuming her husband isn't dead).
But we also have the mc's internal monologue in episode 3 when he makes out with her in the library:
mc: "At the time I couldn't understand Bella."
mc: "The attraction was there, but for her it felt so wrong."
mc: "I remember feeling bad about kissing a married woman."
mc: "I figured she felt the same since she was being unfaithful to her husband..."
mc: "...which, of course, is a very big deal."
mc: "But if I had known the real reasons to her tears..."
mc: "...and to her persona..."
mc: "I wouldn't have kissed her that night."
mc: "I would have called out for help."
There's something more to Bella's predicament, something more serious than we've come to understand at this point.
Of course, depending on your decision, there is definitely one thing that Bella is doing that is pretty terrible. While setting Jill up with the mc, and fully aware of how strong Jill's feelings are for him, she's fucking the mc behind Jill's back. But if you're not on Bella's path, none of that happens, so you can't hold it against her.
Bottom line: Her husband has been gone for 3 years. She's finally decided to move on and start a new relationship. That's not cheating. Finalizing a divorce would be a good idea though.
And for the record, some people feel guilty starting a relationship even if their spouse has died (and that's literally the end clause to a marriage, "'till death do us part"). Relationships and the feelings that are associated with them are probably one of the most complicated things we deal with in our lives, and so many people are not qualified to do it.
