@exxp
It's because it's found out she's a berserker. Berserkers usually are uncontrollable fighters with great strength and such while also almost always never in control of themselves. At worse they never separate noncombatants, allies, and foes and will attack anyone indiscriminately.
Since it seems to be the same here in this case. Saiga showed up at the wrong place at the wrong time to see what happened when she was still in her berserker state, she immediately attacked him without much cause.
@kaezeribato
The King wants MC to make the girl submit and yield without killing. To put it bluntly, the King wants to break her spirit in order to "save" her from execution. All because they want those rare arts/magic. You have to remember that the Royal Family lacks a trump card so the best they can do is get more rare arts/magic to bolster their own forces since each of the big noble families each have a trump card character.