To elaborate, while it's looking increasingly unlikely we'll convince her to be more reasonable, since she seems to view us as an example of The Problem, regardless of what we've actually said (for example, I specifically tried to frame the harm of her plan as harm either to her kind or to other minorities and NOT to white people, yet she interprets that as us simply not wanting to give up any of OUR position), I don't think this means the only other option is to concede. For that matter, I'm not even sure all avenues of discourse have been exhausted yet, but even if they are, I don't see that we need to take this lying down. They may have the upper hand, but we're not yet beaten (also, if we can manage to suss out something more about their Servant's identity through conversation, that would be great).
I don't actually think her 'gesture of good faith' is worth taking, barring some other concession, because it means rendering us essentially helpless against someone who has made it clear that they don't like us (and whose Servant is probably a trickster spirit on top of it). In THEORY, we could take the gamble and hope that she's shocked enough that she might admit to our earnestness, but the odds seem far too low to risk so much (and a whole command seal in the bargain).
Also, I see no reason to reveal the presence of the magic cylinder unless we plan specifically to bargain with it and I don't see that we're in a position where that's useful (she may have little use for it and nothing she's willing to give up in exchange for it)
(Er, I have yet to decide what the next thing to say/do IS, but I do feel very strongly that it's not 'roll over and give up'. Like, no matter what one thinks of the morality of Kimimela's plan, it seems completely doomed to eventually triggering mass civil unrest and possibly open revolt and will likely lead to a worse situation for EVERYONE, including her own people. One possible angle is pointing out how heterogeneous the native population across the US is, as there was certainly no unified front in ownership of the land in colonial times and I suspect they wouldn't even be able to agree how to form one at this point either, though I admit to having relatively little knowledge of US native affairs.)