Tanya goes still for a few seconds. It's unclear if she has absorbed Belmarniss' last few sentences (her orb has recorded them, though.) Then she visibly deflates.

"I apologize. What I said was inappropriate and wrong. My instincts as a soldier should not determine my behavior in civil society, and I will not resort to lethal force if someone tries to affect me with unfamiliar magic, outside of - designated combat zones - places where we could reasonably expect any friendly stranger to approach us openly and not use magic before talking. I will endeavor to retreat out of their range before they finish casting, although unless I start moving right away and can move in a straight line away from them, I'm not likely to get away in the three-second time window." Five gees would barely do it, and Tanya would have to identify the spell as targeting her when she starts moving, and if she's inside a building she can't do it but the spells can't target through walls...

...it's really hard to leave soldier thinking on the battlefield.

"What would you like me to do in the event I detect someone trying to cast a spell on you, and you haven't indicated to me that they're allowed or expected to do so?" Maybe this will help defuse this conversation and help safe what little is left of Belmarniss's presumption of Tanya being a sane person.

"- to be clear, drow are mostly chaotic evil and random people you meet do not particularly care if you continue to be alive. You should continue to project that you are a dangerous powerful adventurer with potentially vengeful friends at all times to limit how much that affects you. Someone who gets up in your business with magic or sharps might be stupid, might be under orders from someone they're more scared of, might be powerful enough to back it up, and themselves might have vengeful friends, and I don't think it's a great idea to turn a cocky mischance into a corpse if you can avoid it, but even with that understood, as a fact of the matter Charm Person is not what somebody will pull out if they are making a serious attempt on your life, it has many other applications and anyone as powerful as you're making yourself out to be would shrug it off most of the time. It's not the case that anyone who can land, let alone try, Charm Person, can in the same motion also kill you, I'm not sure how tough you are under the shield but you've got it up all the time and you're very maneuverable and first-circle spells that deal damage, cast by first-circle wizards who don't have better shit in their arsenal, don't even reliably kill sleeping mushroom farmers.

"I don't suppose you have anything like counterspells?"

"My planet doesn't know yet how to make spells directly interfere with other spells, although it ought to be possible in principle. My shield protects against physical threats, not magical ones! If someone casts a spell that affects me directly and not by creating a physical effect that needs to pass through the shield, then the shield does nothing." This is how confident aerial mages die: to a mage blade wielded at zero range. Under her shield Tanya has a fourteen-year-old petite girl's body. Aerial mages don't even wear body armor!

'Chaotic and evil' sounds like a horrible denunciation of one's own people, and maybe Belmarniss is bitter about something (she does want to leave) and maybe she's justifiably bitter, but - even if people tolerate attacks on strangers, and even in the very worst case where the entire world is made of xenophobic societies like that, Tanya will still need to integrate in one and then she won't be served by instinctively killing people who use magic on her. Also, despite all of Belmarniss's grumbling, Tanya has not in fact seen anyone being impolite to her or vice versa, and the worst thing anyone tried to do Tanya was nonviolently pickpocket her. (And Belmarniss was so upset about Tanya getting in those people's faces...)

Belmarniss hasn't answered her question about what Tanya should do if someone tries to land a spell on Belmarniss. Tanya doesn't know if she's deliberately avoiding it but will refrain from asking again.

"Okay, if you don't have anything like a counterspell - uh, do you think it might help to see them, I was kind of planning to run the duel workshop I'm doing for Johysis as a counterspell practice - then maybe all you should do if someone tries to cast on me is warn me? Maybe knock them down or pull me out of the way if you can? Because, like. My sister might dump water on me, she's got a cantrip for that. One of the kids at the school might think it was funny to get me with a Touch of Fatigue like how they were doing to each other. You can be a lot more violently reactive once we're out of town."

"I should definitely learn to recognize as many local spells as I can! As well as who they're targeting. I've been recording them in my orb but I need opportunities to check and memorize my records, and I don't know if my identification would stand up to any deliberate misleading or obfuscation. Thank you for offering to help me learn more." Deliberately modifying a spell or obscuring it by another one cast in tandem is routine on Earth and the advances and counter-advances are distributed via new orb models, and Tanya doesn't yet know how to handle this dynamic by herself but she still needs to solve it one way or another. Even in acknowledged combat against a definite enemy, recognizing their spell signatures before they finish casting them is an absolute necessity.

...actually. "Maybe I could figure out a way to visualize what the spells look to me, in an illusion, that you could recognize or learn something from? They don't look like the shapes you described in class earlier, but perhaps you can find the correspondence. Then we could describe to each other spells the other didn't see, or make it clear which spell we're talking about when many are cast."

Illusion time! To Earth mages, magic is described by a scalar field of 11 values, with the orbs helping to track magic appearing (being cast) and disappearing (affecting physics) and propagating through space.

"Oh that sounds really fun!"

Excellent, Tanya finally found something that the ordinary civilian magic expert can relate to and is not a bodyguard who is dangerous to let into a city!

She makes illusions illustrating the casting (over several seconds) and ongoing behavior (where applicable) of the spells she has seen often enough to try to factor out the variables changing between casts: Light, Root, Message (from the lesson). She also recorded Share Language and Tongues, and some other spells she happened to see being used in the city, but only once or twice each so she's less sure she isn't capturing irrelevant details there.

"Oh wow that is completely different from how things show up to Detect Magic. What do all these eleven things represent?"

"The eleven factors were found empirically, by varying spells and identifying what differences mages can and can't sense. In other words, there may well be a more complex underlying reality, but our only magic sensor remains a mage's mind and mages appear to perceive these eleven factors. It's even possible that there are more factors I could detect that my magic can't produce and so no mage on Earth ever encountered. I'm afraid I don't know the complex theories and empirical models that explain how spell effects relate to these data, I can only recognize and memorize patterns of specific spells once I do know what they do."

"Huh. Can I see Root and Message next to each other and then Light on the side?"

Certainly! Tanya can make as many illusions as Belmarniss wants. ...alright, she can't make thirty illusions, but she can make a few large ones and change parts to show different things. 

The illusion can be annotated with the caster's location (corresponding to a rough midpoint of their head) and the presumed target location (easy to determine in case of Light). It can be slowed down or frozen at different points in time to show the evolution of the spell is being cast. Several different recordings of the same spell can be shown side by side with the (comparatively minute) differences highlighted. 

Root and Message are both transmutations and Light is an evocation! Is that reflected at all here? Maybe! Suppose she casts some more cantrips to see how they relate.

Tanya was hoping Belmarniss would tell her that! She can show her what her cantrips look like practically in real time. (Feeding the magic detector's live data to the illusion spell is a usecase specifically supported by her orb. Radar operators use similar spells to monitor airspace from the ground.)

This is so neat and Belmarniss will play with it all day if Tanya has nothing better to do.

Tanya has no specific other thing to be doing. They probably shouldn't delay their expedition for weeks while Belmarniss plays with this, but a day or two is well worth it if it helps repair Tanya's good standing. Tanya will also remain available for spell-illusions when they're on the surface!

Eventually Belmarniss decides that it's mostly tracking things orthogonal to spell school but believes she could get a better than chance guess at school with more data. Which is great because Detect Magic mostly only wants to tell you about strength and school! This warrants further study but they should have dinner now.

More mushrooms?

They're pretty near the river and can get fish with their mushrooms if Tanya likes fish?

Tanya does like fish, and more relevantly it's important to maintain variety; she doesn't know if these mushrooms are a full and nourishing diet for humans from her world.

"I don't think people who have humans find that they are very hard to keep alive but it might be related that humans are an expensive exotic so people who have them can probably afford more plants and stuff." Grilled fish and mushroom skewers for supper.

Tanya will politely avoid passing comment on the exotic kept humans during dinner conversation. Grilled fish and mushroom are good. Plants are also very important but she thinks mushrooms actually substitute for those, it's meat they might not replace well.

"Okay, so, I can buy you another night in the hotel, but it does add up and if you're good to stay awake another eight-or-so hours and be real quiet during them, I can also take you home and let you have my hammock after I wake up, and then I can come get you in time for the counterspells workshop. I do need solid sleep to be able to hang new spells when I get up, though."

"I can stay awake another eight hours if I have to, I'm used to dealing with irregular sleep schedules." Belmarniss's home is presumably safer from random would-be robbers than a hotel. She could also use the time to talk to someone else, like Belmarniss's mother, but she's not offering and Tanya won't push. "Would a little illusory light disturb your sleep?"

"No, why would it?"

"Some people find it easier to sleep in total darkness because their brain associates light with the sunrise, or at least with the start of daily activity, so the light wakes them up. It makes sense that doesn't apply to you but I wanted to make sure."