There's no reason to think she killed anyone else besides said drunk, since the person on the same table as her survived.
You're going to assume that a massive explosive spell she unleashed, that was powerful enough to completely demolish the building and create a plume of fire and smoke seen across the capital, is somehow selective enough that the saint from the hero's party and at least 9 other people were selectively ignored?
Notice also the king said "citizens". Plural, meaning more than one.
And even if she really did because of the author's stupid writing, I'd still side with her - rule of the strong and all that, remember this isn't the lame modern day world after all.
Nothing in the story suggests "might makes right" is present in the story, you're just making random shit up to side with Aiza.
And ancient societies has had "rule of law", it's not some "lame modern day" invention, see Hammurabi's Code.
If she were actually strong that is, but the author is also stupidly backing out of that part - despite her supposedly having been strong enough to be sent on a mission against the demon lord, now she's cowering in front of some lousy guards or knights. Why didn't they send those to kill the demon lord then?
If you had actually read this chapter, you'd understand that they were only given the title of "hero" and that the Alliance doesn't actually care about defeating the Demon King.
And it has already been explained (back in chapter 16) that Mills' skill is an instant kill ability. From that you can gather the goal was to get Mills to within range of the Demon King and assassinate him.
The author is just running with the "hero party is useless without mc" trope and making a nonsensical mess out of it.
Or you know, you didn't actually read any of the chapters and comprehend it. Because it sure as hell looks like you didn't.