My brother-in-law always tells me "I love you man" and gives me a bro hug. Creeps me the fuck out!
But my sex life aside, and back to Jill & Bella, their interaction when they are sharing Bella's bed (since the mc's on the couch) has been discussed quite a bit here, and many believe there are sexual overtones:
Jill: "Is something wrong?"
Bella: "No. Nothing's wrong."
Jill: "If you say so."
Jill: "It's not gonna happen again."
Bella: "..."
Bella: "I thought we had an understanding."
Jill: "We do. That's what I wanted to assure you of."
Bella: "I don't need to be reassured. I need you to stop talking about it."
Jill: "Wow..."
Jill: "Fine! But I wasn't though."
Jill: "And it's not my fault, I was going to sleep on the couch."
Bella: "Can we just sleep?"
Jill: "I'll take the couch instead."
We obviously don't know what it is they are talking about, but somethings making them feel awkward, and since Jill mentions she was going to use the couch but couldn't (because the mc took it), and that's what's triggered the situation, it seems very likely that they had at least one sapphic adventure in the past.
It may or may not be related to Bella's thoughts when she's yelling at students in the library (although the yelling is due to her being jealous of Jill with the mc):
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 bit where she mentions she shouldn't be intimate with friends, kinda excuses it as "different", and then dismisses it as having already stopped... Is she just talking about the mc? I don't believe she's talking about the Burkes because it sounds like she's shot down all of Stephen's advances, that kinda only leaves Jill...
So yeah, something really looks to have happened between Jill and Bella, and I can't see any reason to vaguely throw a few lines in that hint at something only for it to go absolutely nowhere, so I believe there really is a potential for some Jill/Bella/mc three-way action before the end of this story.
But I really don't expect Jill and Bella to "end up together" under any scenario.