I'm pretty sure she was quite explicitly ordered by Sakura not to kill him....
Zouken created some kind of cheap "copy" of her, I think.
Yeah. They showed up to find Caster holding a blood-covered Rule Breaker and Kuzuki dead, and then Saber killed Caster out of disgust.Though if memory serves, it was Saber who killed her.
I've tried reading it, but I couldn't make any sense of it whatsoever.