Interesting she only mentions James' name twice in the whole game. The scene in the library is vaguely telling:
isa "(I can't lash out at students like that...)"
isa "(...)"
isa "(I did the right thing.)"
isa "(This was for Jill.)"
isa "(Married women don't fool around with young students.)"
isa "(...)"
isa "(They aren't intimate with friends either...)"
isa "(But that...that was different!)"
isa "(It doesn't matter... I've stopped it.)"
isa "(Please, James... Forgive me.)"
isa "(Please, just come home again...)"
isa "(It's been long enough now.)"
She's setting the mc up with Jill even though she wants him, and we can see she's jealous of Jill with the MC in spite of herself.
When she talks about not being intimate with friends, but that she's stopped it, maybe she had an affair with Jill that wasn't just a one night thing. I definitely don't think she's alluding to something with the Burkes (that's just Steven's fantasy), and we do know that something happened with Jill.
"It's been long enough now" means it probably has been 3 years, not just a recent thing.
But I can be swayed to believing he's alive, and because she's asking for forgiveness here, and then saying she forgives him in another scene, I guess she probably started it (had an affair with Jill), he reciprocated (had an affair too), and they split up. Since it was her fault, she feels guilt rather than anger, hence the whole nutty disposition.
But none of that really lines up with the MC's exposition in the library, "call for help" etc.
I dunno...