How... anticlimactic.
I personally say keep UK alive. At this point, she's teetering at 1 HP. So long as she doesn't lash out against anyone, I can see her being useful. If anyone kills her, good chance that person is very scummy. However, no one is to heal her and she is not to attack anyone else unless we've agreed that person is scum. If we do ultimately decide UK is scum, we can kick her off. If she gets tsundere again with someone, we just kick her out to avoid problems. After all, with her spellcard more or less spent at this point, she's harmless unless we let her be dangerous.
Now, as far as Edible. I do not believe UK's action was useless. On second thought, I'd like to know what Edible was expecting. Last time I checked, he's still at full HP PLUS the spellcard. Perhaps if UK was Marisa or Yuyuko, I see why he'd do that, but that's getting meta. I demand to know three things:
1. What does your spellcard do?
2. Why did you activate it? I mean really, FULL HP. Even if you were severely hurt, if anyone decided to attack you at that point, we'd know that person was scum.
3. Do you think Roukanken now thinks you're scum?