Did she even say how she would join the war? You’re all acting as if Nacht agree to fighting in the war and killing people. Since the princess never stated the role she would have if she was to join the war Nacht can just do something as simple as giving low ranked items to the princess as that would count as having joined the war.
Why are you immediately jumping to them killing Aisha? Just attacking and harassing them during their journey would be more than enough to ruin any enjoyment Nacht might get during their travels. Even if they don’t do stuff like that they could issue a country wide edict that would make it impossible for the two of them to stay at inns or buy food or equipment. Even if they left that country it wouldn’t stop as the other countries also wouldn’t look favorably at them for having released the demon clan.
Lastly the only disadvantage that she was sweating over was her mistake being revealed (which she is embarrassed by) and that she would possibly have problems going places with Aisha if her secret got out
I genuinely do not think you understand what Nacht even is....
And I'll reply in order.
1. "She can give them items, that also counts as joining the war" -- that's roundabout and pointless. If that's the aim, it is terribly written. How is that a better argument?
2. "Why are you immediately jumping to them killing Aisha? They can just harass them instead.." -- do you even listen yourself talk, mate? They'll HARASS THEM? They'll "bar" entry to them from local services? When she can destroy an entire country with a flick of her finger?
Do you just think a demigod like the MC, would just "take" the harassment and do nothing about it? Are you out of your mind?
Do you think any of the ruling bodies would
want to "harass" a demigod, and expect to live to tell about it? Are you serious here? Heckling a demigod is retarded, and only reserved for F-tier villains.
3. "Other countries also wouldn't look favorbly at them for having released the demon clan" -- they'd also realize antagonizing something that's even worse than the demon clan, an existence that is otherwise affable and a bit ditzy, is a lot dumber than "harassing them". A ruler that is not an F-tier villain, would realize it's a lot better to draw Nacht into their fold, rather than antagonize her.
4. "she would possibly have problems going places with Aisha if her secret got out" -- that's only true because of what people are complaining about. The MC is a walking nuke, but acts like she's a normal person. She'd have absolutely no problem if anything would to get out, fact is -- it already has. She was threatened just this chapter, wasn't she?
Literally everything you wrote only makes sense, if you want the MC to act as a stereotypical Japanese MC who doesn't understand their own position: Having all the power in the world, but still having the mentality of a powerless citizen.