Belle really did wish she had more information. While she had been reading one of her favorite stories before she had gone to save her papa that was fiction, she also enjoyed reading up on things that were being discovered, of learning all there was to learn around her. Belle didn't discriminate in her reading as she loved learning and having information. And so the fact that she didn't know? Well, it was strange. And upsetting in this situation as it meant she couldn't be as helpful as Emma had been for her. But she would do the best she could as that was all anyone could ever really do in this sort of situation.
At least he seemed to grasp that, while impossible, it had happened. Which was good because Belle really didn't know what she'd be able to do to help him adjust if he kept insisting upon insanity. But really, there were all the signs pointing to something had happened and while there was no logical explanation, it still had happened. That basically was how Belle had looked at it. She at least had the benefit of dealing with enchanted objects so magic was more believable than it would have been had she shown up before getting to the castle.
"I am uncertain what he would do with your soul. His goal is actually to destroy humanity and wipe us from existence all together. I was told that we are not required to fight, but if you wish to, there are classes which are offered to help. Though... apparently there are demons that can possess you if you do not have an amulet like this with you." Showing Enjolras her amulet, Belle folded some hair behind her ear, "If you are feeling better, I can take you to the complex. It is set up for people like us who show up from different worlds and times to help us adjust and give a place to live where we do not need to worry about rent. They have the amulets there."