You know, we really do need to pause for a moment and appreciate what Yokochou has managed to pull off. 99.9% of the time OC's added into large canon series just do not work, nor are they accepted by the fans. The fact that she's derived helps no doubt but the glee we all experience any time that child shows up can not be understated.
Well, it's implied that Yuuka's actually a pretty nice person so long as you don't make her mad. THAT is when the "Smiling Monster" who thinks genocide is a fun Tuesday activity comes out to end you. They wouldn't allow her to shop in the village if she was a maniac 24/7. Yuuka's got a temper, to be sure, but it's very easy to not trigger it. Don't trespass on her land, don't mindlessly destroy flowers, and be polite around her.