Tanya sets her orb to replay everything he said (appropriately sped up) and squeezes it for meaning.

So I suspect your ‘working understanding’ is badly wrong… I intend to try to explain properly in more detail.

What does he think her understanding of the gods and their treaties is? What is 'gods and their treaties' even referring to here?

She assumed the local religions were as disconnected from reality as those on Earth, but she does know of one being who styles himself a 'god' and who sometimes empower people's magic and pretends it's a 'miracle'. And where there's one, there could be others. There are all kinds of philosophical treatises about the properties a singular God must have if He existed, which proves He doesn't since Being X clearly doesn't qualify.

This planet's locals seem to be religious the way people are on Earth. They talk about 'gods' and 'angels', but when they call 'heaven' like Tanya might call up Regional Command they get a normal person and not a Being at all. Someone who takes the time to remind them of the long list of allied and enemy gods in the pre-battle briefing. Someone who emphasizes there are conflicts and treaties between the gods, that he serves one god but others have their own servants. The same gods who magically empower people on this very planet. And then he underlines that information about other planets including the ones the gods live on is not given out lightly to the people living here, and that he can only talk to her about the things that she already knows.

Maybe her earlier idea of colonialism was right. Maybe these 'gods' are metonyms for powerful planets and nations, playing pretend with the credulous natives and warning her not to ruin the charade. And maybe, just maybe...

Maybe Being X is one of them.

They mentioned resurrecting the dead and she dismissed it, but didn't Being X reincarnate her at his whim after she died?

What else did he say?

“It is completely reasonable to not know anything at all about this, especially considering your background!”

Does he mean her background as in - her actual background? Is he referring to the fact that the first world she lived on had no magic? ...Is he implying a claim that all magic comes from the 'gods' and is bestowed at their whim, and her first world was a low-intervention one?

Too much speculation. She could spin in circles like this forever. Set it aside for now.

But anyway, let’s discuss your planet first.  So… I may have actually heard of your planet ‘Earth’, it’s not one I’ve specialized in knowledge in…

'May have'? 

the most recent thing I read about it was a major industrialized war between the colonial empires centered on the continent of ‘Europe’.  This war started… 8… no 9 Earth years ago...

It's not fair to describe Germania as a colonial empire, they're practically the only Empire on Earth that doesn't have significant colonies, but he could be generalizing or - referring to the god-nations' nature again? Assuming 'empires' are naturally made up of 'colonies'? Never mind, it's probably not important.

The war started with the Legadonian border violation in June 1923 but it wasn't a war between major powers until the Republican invasion a few months later. Five years before then was... the Third Balkan War? What does that have to do with anything?

In any case he's implying she is missing between four and six years of memory and - it seems frankly improbable that her body wouldn't changed noticeably, unless she arrived here by near-lightspeed travel which... for all she knows is how interstellar teleports work... Wasn't Alpha Centauri about that far away?

I recall specifically the comment that with a better knowledge of writing treaties, the European powers could have avoided the war,

Anything is possible, she supposes, but when nation after nation unprovokedly attacks you without even a casus belli it's rather hard to keep faith that they wouldn't have just torn up a treaty that didn't suit them! Treaties can make it not in your interest to attack but that requires rational judgement; the kinds of people who start wars tend to be insane warmongers who enjoy war or who think it can redeem a nation's soul or some such claptrap.

an assassination in one minor country triggered smaller countries to go to war which drew in bigger countries via treaties until the entire continent was at war.  Does that sound like your planet?

...no? No, it really doesn't? 

But it does sound like a certain other war, though, on a certain other Earth... 

Have these people been spying on her original Earth? And their last reports are a century old? ...and they didn't notice that World War One had no aerial mages and that Earth had no magic - no, surely that makes no sense. Not unless the report on 'Earth and its recent war' was all of three pages long and Jon only read the executive summary. Which is a worrying possibility she can't quite dismiss, but -

If her arrival here causes them to take another look at that Earth, what might the unholy marriage of actually-modern military technology from the year, uh, 2027 (or is it 2032 by now?) and teleportation and mind control magic produce? On the other hand, Being X already knows about it, so it's presumably a lost cause to try to keep it a secret even if she had a stake in doing so.

If she claims to be from her first Earth she can admit to recognizing his story, but sooner or later he'll realize (or reveal he knew all along) that that Earth has no magic and she'd be exposed as a liar.

If she says the story doesn't match and describes her (second) Earth accurately, it may enable him to find it if he hasn't yet. Part of her is tempted to say that they already have Being X messing around so surely other 'gods' have to be better than that, but of course that's nonsense; there's plenty of ways for 'gods' to actively harm people if they wanted to. Introducing this interstellar civilization to Earth while Earth is behind on magical development is likely to end with Earth as another colony kept poor and ignorant.

Inventing a completely different world... no, there's no way she can do it on the spur of the moment.

Refusing to answer will presumably fail her this 'interview', even if they don't outright turn hostile, and there's a good chance Jon or his superiors can find her Earth anyway with some magic or technology she knows nothing about.

It is extremely unfair to be removed from your social and legal context and support networks and then to be asked to choose between your personal wellbeing and that of your entire planet.

...her missing years (?) still have to be accounted for and if she spent some of them on this planet then she may have told already told someone about Earth. They will certainly investigate her past; in fact it would be suspicious for her not to ask them to do so as part of her payment, she already told Terendelev she wanted to find out how she came to be wounded and unconscious outside her city - or was she only planning to tell her that...

Ugh. Tanya really doesn't want to break off relations and she wants to be caught in a lie even less, so that leaves telling the truth. Cooperating with the local authorities is surely a good thing, and she is not at all betraying her comrades' trust and her officer's commission by making a decision that just happens to preserve her own life? Isn't the argument for keeping mum essentially a conspiracy theory at this point, and not anything that she could prove? She can imagine herself making this argument before some future hypothetical court. (She can also imagine the court ordering her summary execution, but she must save her life today before she can save it tomorrow -)

Clutching that flimsy justification, Tanya slows down from her frantic mental acceleration, which was in fact starting to exceed the so-called safe limits and has already caused her heartbeat and breathing to speed up rapidly.

"That description matches only partially. The war started with an unprovoked border violation and later grew into a major conflict when a different nation invaded us. I never heard of an assassination being pointed to as a cause for the war. The war has lasted less than five years even counting from the earlier conflict; it is possible that I am missing memories of a long period, since I do not know how I arrived on this planet and am definitely missing some memories for an unknown reason - I assumed it was months at most because I would have grown noticeably over the course of a year but if interstellar teleportation obeys the speed of light then maybe I spent those months being transported?"

"...do you happen to know the current date on Earth?" She really should have thought of that question earlier.

He can tell she is using some sort of subtle haste effect on herself, and it still takes her a bit of time to respond.  Among the innocuous explanations: she is considering several perspectives on her war to see if any matched his brief description, she was disoriented by the apparent lost time, she is processing some feelings.  Among the less innocuous explanations: she is worried about how a being claiming to be from 'Heaven' connotations might take the fact that she was involved in a war ('Some of his word associations for 'Heaven' in her native language are a bit worrying), she was crafting a nuanced lie, she was struggling with memory modifications from demons/Fey/Geryon.

He wants to help her and work together effectively with her... but maybe it would be best if his caller lets this calling expire in the hour duration and calls a different specialist tomorrow.  For his calling, Iomedae would have had to juggle multiple priorities picking out a good spotter and someone that could help someone from an unknown planet orient effectively.  A follow-up calling could take advantage of what he has learned and the lack of extremely pressing need for a spotter to get someone more suited.  In which case... he should get as much context as he can so Heaven and Iomedae can figure out which specialist to send and position Tanya to have reason to trust whoever that specialist ends up being.

"Some methods of interplanetary travel would have a travel time-" if her planet knows about the speed of light it might only be a matter a time before they figure out mass energy conversion, which is really alarming but he needs to focus, he needs just the right level of vagueness that avoid expenses. "-Earth is too far away for a speed-of-light travel time to account for such a small discrepancy.  I will note that on this planet there are many spells that could effectively achieve stasis, including spells as low as 6th circle spells, such as the combination of Stone to Flesh and Flesh to Stone to petrify and un-petrify someone.  As for your other question... a moment...." 

He reviews this question carefully.  If she isn't from the Earth that he knows of... he actually hasn't said anything expensive yet, vague facts and descriptions are cheap.  The things that would cost dramatically more would be anything enabling interplanetary travel.  Names are a notable liability, among this planet's known spells, a modified, improved Discern Location that doesn't require having met the person would provide enough information for a Wish or Interplanetary Teleport.   The exact year... maybe has some slight liability with divination spells, like helping to direct a legend lore, but shouldn't be expensive either.  He takes another moment to check his reasoning, then shifts through some advanced mnemonics to convert the Celestial date methods he knows to Earth calendars.

"Sorry for the delay, I was mentally double checking for any subtler implications or consequences of sharing that information as well as actually doing the mental math on date conversion.  The date, on the European calendar, is 1923."

He'll hold off on more specificity until she gives him a good reason.  Thinking of the European Calendar, has got him thinking about European language.  …doing comparisons on her language versus European languages... her language is definitely a European language, it's almost exactly like one language in particular, but has some very slight differences from that language... he's pretty sure it's not just regional dialects... word associations to bring proper nouns to mind... okay now he's confused!

"I noticed something else that I need to think through."

A pause.

"Can you give me some small samples of other languages from your planet besides your native one?"

Truespeech is so much better than telepathy if you know the tricks to really bend it and stretch it.