Hmm... I still don't understand how is Gaia not full of crap. The whole reason to have a demon lord is already unstable, but let's say it's okay, and simply a rule of this world that cannot be changed. Okay. The demon lord not knowing who the fated person is? Pass. I don't really understand why since the demon lord is the most unfair existence in the world, like being full cursed and do everything to have everyone to live peacefully.
But why not give at the very least a hint to the other worlders that hey need to find the demon lord? That's not even fair, that's full scumbag decision right there! If you don't know you're supposed to meet him, most people won't go meet him! Most people won't even know that they need to! I could understand why let the demon lord in the dark considering the matter, because the summoned one should have the choice to do what he wants and what he choses, but you're not even let him chose, you prevent the summoned one from even knowing its options! You just dump someone in the world, with usually less than a year of deadlines before the demon lord's madness!
And why drop them randomly like that too? Why not deposit them at least a bit closer to demonic territory so that they at least have a chance of learning about demons, of getting possible hints? Because the only reason Suzumi got hints is because she absolutely wanted to go back, but most people wouldn't give a damn if they were dumped overpowered in a world of magic...
And what was that story about getting an other worlder killed because the demon lord was near madness, so everyone was hurrying to help...? That doesn't even try to make sense.
Anyways, if I were her, I would definitely bargain to get something like 5-6 digits of maximum mana, have the right to use space magic, even ask for time magic too because why not, go live a happy life as purple soul's bride for some 7000 years, and then go back to our world with intact memories, mana and spells, and live another happy life of adventuring and whatnot. I really don't see the difficult choice here, but I suppose it depends on the people? ^^