Bella is hanging out in a Jarvis - the familiar one - handwriting a nonaggression proposal-slash-bribe. Has to be handwritten. Damn fussy demons. At least it's okay for her to conjure rather than personally harvesting the weird ink she's supposed to use.
[I'm a human. If you'd be willing for me to put us someplace where obsequious demons aren't going to walk in on us at any moment, I will be happy to turn visible.]
Her preselected Canadian wilderness is in use, so this is Nevada wilderness instead. She lands them near her cactus landmark, turns visible, and turns around once, arms out. "This is me."
"Nice to meet you properly. Welcome to Nevada. I'm not going to strand you here, but in case it makes you more comfortable, there is a highway, three miles that way -" she points. "With a rest stop not far from there. So, yeah, this is me, I'm a human, I'm very magical." She hops into the air and spins around again.
"I told you, I don't know until I try it and see if it works or not, and if I'm going to try it I'd like to be a little more remote than three miles from a Nevada highway, such as Mercury, and I'd also like to have a plan for what to do if it works."
"You can give me information," says Bella. "Everything you know. Even if you don't have complete understanding of some thing you've heard or seen or read, it could inform my own research."
"So it would seem, yes. I don't suppose it helps any that I clearly could do something awful - to you, to anybody - and instead I'm spending my time poking around powerful hellgods because they've been making mental patients of innocent people? This doesn't suffice to demonstrate that I have benign motives?"
"I don't suppose I can solve this problem with bribery?"
"Glory brain-sucks people a few times a month," says Bella. "I don't have very long to gain your trust the old-fashioned way by hanging around and not doing anything evil, and she will definitely notice me if I teleport her next victim away, and I don't currently know how entangled she is with you, so I don't know if my first idea for dealing with her in a crisis situation will hurt you or not. Resurrecting the dead is more inconvenient and time-consuming right now than usual, and even the victims who don't wind up dead are a hassle to fix and don't look like they have a pleasant time on the way there or subsequently, so allowing her to go about her business is not on the table. If you really want rid of her, you want to talk to me."
"Look. Ben. I'm sure having her intermittently possess you is very annoying and you just want it over with without having to endure any further hassle. But I don't think you would want me to just teleport you to Mercury and attempt to pull her out of you there if you thought about it. I don't know what will happen if I do that. For all I know, you will die as soon as I do it because of some kind of dependence between you and then I have to go haul you back which could take me a while, or she'll triple in power and be strong enough to give me a difficult afternoon once you aren't attached to her, or she'll go terrorize her original subworld and then I have a difficult rebellion project on my hands, or something. Some of those outcomes are not great for you."
"She can't get back to her original hell dimension," he says. "And I thought you said your magic could split us. Either you can do the impossible or you can't. How am I supposed to know exactly what impossible things you're claiming you can do when you won't tell me what they are or how you're going to do them? If you don't even know that I can live through it, why are you suggesting it at all, and especially why did you suggest it without mentioning that up front? This is not helping with the trust thing!"